From PBS (via Matthew Cobb), and inspired by Richard Dawkins’s The Magic of Reality, we get a short video explaining to non-scientists why there was no first human. Matthew tells me he’s going to show it to his students, and it’s a good didactic tool. Have a look:
There was no first human
August 25, 2014 • 12:08 pm
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Excellent!
Reblogged this on Adventures in randomness and commented:
Excellent video with great explanations!
Very good. Just like this interview with Richard Dawkins!
But (I was watching this on mute) I found the random breaks in the subtitles very irritating.
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I heard Richard Leakey give a talk about human evolution where started with modern humans and went back in time asking the question when do we have an ancestor who would be noticed walking down the street in modern clothing. It was quite interesting.
I don’t like the video. It is patristic or anaginic ladder of life evolution (with only one little side illustration on cladistic speciation). I think it completely misrepresents modern thinking about how evolution occurs.
I agree … didn’t really address speciation, which it needed to do.
Great video.
I was curious to read some comments on it and man… the number of “why are there still monkeys then?” is truly dispiriting…
(I know, youtube comments always are dispiriting but still… I’m baffled, and sad)
I’ve been battling these clowns on Twitter for months now. Whenever I see “If we evolved from apes, why are there still apes?” I throw a curve ball at them and say “We didn’t evolve ‘from’ apes; we ARE apes” — then I attached this handy link from the Australian Museum:
http://australianmuseum.net.au/Humans-are-apes-Great-Apes
Cross ref to Neil Shubin’s “Your Inner Fish” book, and the spun-off TV programmes.
Or, as my signature line on another website says, “Birds are not dinosaur descendants ; birds are dinosaurs, for all useful meanings of “bird“, “are” and “dinosaur“.
Another spin is to ask them ‘where are your ancestors from?’ Suppose they answer that they came from Italy. Then you say ‘well, why are there still Italians?’
Since these people are more than likely Christians, a good comeback is to say “If Christianity came from Judaism, why are there still Jews?”
Or substitute any cultural phenomenon to your liking (e.g., cars, planes, etc.)
The problem with cultural changes is that one can get side tracked, particularly with the one you started with. Strictly speaking the argument works, but sometimes the difference between logic and rhetoric is important.
Essential and missing understanding. Had one of those frustrating conversations this weekend when I was asked what the odds were that a male AND female mutation would come up at the same time in the same place. Otherwise humans would have died out from the start since there was no one to mate with …
When origin of sex comes up, one might divert the discussion to conjugation in the green algae Spirogyrs. That should disorient and confuse them.
This video was made by “It’s Okay To Be Smart.” That is, Joe Hanson; the creator and host. He’s a PhD biologist and a future Rock Star of science education. Check out his other YouTube videos @ http://youtube.com/user/itsokaytobesmart
The one about kissing is great!
And he didn’t forget a cat🐯
Thanks for the link, CJ. From the Youtube comments, it appears Joe saw the discussion thread over here at WEIT and really enjoyed it. I think both websites will get some new fans.
I think I know why creationists and other people fall on the “why are there still monkeys?” meme. They get confused by these depictions of the generations as a big continuous single line of son-father-grandfather-….. I know it’s something so obvious for the rest of us, that the producers of the videos don’t see the need to explain that the line is just one thread in an intricate web or population. They (creationists) don’t think in terms of populations. They think the depiction is saying that, at a certain point in time there was just one individual who gives birth to one son (without partner!!!) and all of them die at their time with no other descendant than the one down the line.
The producers of material on Evolution should lower the level for creationists and simple people. When showing these lines of descendants, take a couple of seconds/minutes to explain the population and genetic pool thing, and how some “threads” can drift away to form other species.
Don’t overestimate them; they are easy thinkers. That’s why they have no problem accepting that all the species on Earth can fit in a wooden ship, or that the planet could be 6,000 years old. They don’t even know (or even try to know) how gravity works or that the sun is just another star.
Is this condescending? Yes, but there is no other way to say it.
You make a good point. When explaining evolution we tend to assume that people already know some of the things we take for granted.
There is also the problem of active resistance to the information being presented for evolution. A person like Ken Ham has been exposed over and over again to detailed explanations of the evidence. He instead finds as many ways as possible to make his Biblical nonsense seem somewhat plausible using sciencey sounding just so stories.
“the producers of the videos don’t see the need to explain that the line is just one thread in an intricate web or population”
Please watch the video again.
Hint: It’s there in plain view.
I wonder how the female students will react.
Yeah, dude here, but it was still pretty jarring.
Also that first frame of the video shows both the before and after primates with Caucasian levels of skin pigmentation. Yeesh.
Both species were in Africa and would not have done well, especially H. Sapiens, to the extent it resembled red-headed northern Europeans.
Unfortunately, the video just sweeps the sorites paradox under the rug. If (1) classical logic holds, and if (2) humans now exist but didn’t always exist, then there MUST have been a first human.
I presume that no one here will deny (2). People will be inclined to deny (1), I imagine, but the problem is that all of the nonclassical responses to the sorites paradox come to grief: either they don’t eliminate the sharp cutoffs they’re intended to eliminate, or they redefine logical vocabulary in Orwellian ways, or they accept logical inconsistency. So it’s classical logic or bust.
For details, see http://plato.stanford.edu/entries/sorites-paradox.
Hmmm,the link you provided provides a couple of good ways around the sorites paradox. The article mentions that there is a good case to be made simply for denying groups of middle premises in a long sorites.
That’s in fact what the video is doing. It’s simply saying vagueness is inherent to the concept of a species. It also says that might be a good thing. The entire video is exactly what the article you linked to talks about in section 3.2. That section also mentions that this method of resolving the sorites is over 2000 years old.
I think you’re right to focus on section 3.2 of the article (the “epistemic theory”), since it’s the best response. But the epistemic theory says that there ARE sharp cutoffs: for example, between prehuman and human. It’s just that we can’t know where those sharp cutoffs occur. Nevertheless, the sharp cutoffs exist: there WAS a first human (or a tie for first), someone whose parents were nonhuman. That’s implied by the epistemic theory.
Well, we could just bite that bullet and go for some kind of nonclassical logic as the end of 3.2 indicates. But I don’t think that’s really necessary.
I don’t really think the rules of logic are “out there”. The fact that classical systems of logic fails to deal effectively with the sorites doesn’t mean we have a real paradox. Sometimes a system of logic just doesn’t cover a problem very well. Sometimes human intuitions are better than the system of logic we are working with.
For instance, propositional logics say the paradox of material implication is a valid form. Our intuitions say it is not. The problem is that there are features of language these systems fail to capture and not with our intuitions.
Likewise, classical predicate logics are great for all kinds of stuff. But since they define predicates as the sets of members in their extensions, they sometimes fail to meet our intuitions when applied to intensional predicates. Again, this does not mean that our intuitions are wrong, just that they are not covered by predicate logic.
So, if we have an intuition that vagueness is inherent in the concept of some predicate, such as “is a human” and that this actually helps us understand something about how the world works, we can do this. The sorites cannot stop us.
Logics are tools, not metaphysical principles. And yes, I realize I am going against a long tradition here. I would recommend reading the final chapter of John Nolt’s Logics which is a discussion about whether there is such a thing as a “correct” logic. Nolt would argue that logics are created to do jobs, and the one that does the job is the right one.
Sometimes human intuitions are better than the system of logic we are working with.
Be careful: Woo-peddlers will happily help themselves to that line!
Much more importantly: The classical logic I’ve been appealing to is none other than the logic you rely on in your comment. Please see the very simple argument in #23 below, and let me know what’s wrong with it.
[Sidebar: If we understand what material implication is (if we understand its truth-table), then there’s nothing “paradoxical” or “invalid” about it. Rather, the worry is a semantic one, namely, that material implication doesn’t capture what’s meant by many natural-language conditionals.]
Nothing woo-ish here at all. When you actually study systems of logic, you run across examples how systems of logic fail to conform to careful intuitions. I think there’s a lot of power to squeeze out the woo in that “careful”.
And while you are correct that the problem with the paradox of material implication is a semantic one, that a truth-table cannot capture the full meaning of “if…then…”, I think my point still stands. The truth-table semantics of a conditional is a part of propositional logic, and it works very well most of the time. But when it fails, we say the failure is with it, not us.
Likewise, classical predicate logics are insanely powerful. Defining predicates and relations extensionally as sets of members allows for incredible rigor. However, there are some cases where doing so will make an argument valid when our intuitions judge it invalid. “Clark is Superman. Lois believes Clark can’t fly. So Lois believes Superman can’t fly.” is a traditional example. Predicate logic says it is valid, our intuitions say it isn’t. And our intuitions are right.
And that’s another point about woo. I think just about every time we are going to say that a system of logic has a problem, we do so because the system is too permissive and our intuitions are more stringent. That’s true of material implication paradoxes and also true of the Superman argument.
So when classical predicate logics say the “first human” argument argument is valid or or that I can’t make a person bald by pulling out individual hairs I really can just say those arguments are invalid and walk away even though for all kinds of arguments predicate logic is awesomely useful. I really can say that for some predicates we cannot assign some individuals to the class of members that have that attribute, or to the class of members that don’t have that attribute. And this is not just an epistemic problem, that the individual really is a member of a class or not and it’s just that I can’t know whether it is or isn’t a member. It’s just the way some predicates are. And yes, I just threw out the excluded middle. So what?
Does it sweep the sorites paradox under the rug, or does it point out the problem with thinking that classical logic is unassailable?
Unfortunately, the nonclassical responses fail not because classical logic is assumed to be unassailable, but because the the nonclassical responses either fail to eliminate sharp cutoffs or else offer a cure that’s worse than accepting sharp cutoffs.
If you’re interested in why, I recommend reading Timothy Williamson on this topic.
I’m sorry, but this strikes me as an awful waste of time on a matter that’s merely semantics. There are no sharp cutoffs. Period.
But if philosophers want to spend their time deciding when an infant becomes a child becomes an adolescent becomes an adult, well, that’s their right, I guess.
Please see #23 below, and let me know what could possibly be wrong with my very short argument there. I promise it won’t take much of your time, and it won’t waste any of it.
(By the way, the point of the epistemic theory is precisely that we shouldn’t try to discover, or decide, where the sharp cutoffs occur.)
I’ve read it. All I’m getting from it is that Classical Logic is basically useless if it leads to claims which are false in the real world. Which means it’s basically useless, period. Because how can you know when it’s right and when it’s wrong? One more concept philosophers have tried to impress us with that falls flat on its face. (Pardon the Kilmer-ish metaphor.)
Either that, or you’re just trolling here.
Seriously? That’s all you’re getting from #23? Some who commented here at least admitted that #23 gives us reason to reject
(1) EVERY human that has ever existed is the offspring of human parents who belong to a previous generation.
John Scanlon said (falsely) that the video never asserts (1), but at least he admitted that asserting (1) would be a “dumb mistake.” But you say you can’t make heads or tails of #23. How sad.
Quick question, concerning one way of defining a distinct species on the basis of its “reproductive isolation” from other animals. Would it be fair to say that at any point along the “photograph stack” of geneology that a particular individual “B” could produce viable offspring with an ancestor “A” from X generations past* and a descendant “C” from X generations in the future, but that “A” and “C” could not?? (Presumably the time difference X couldn’t be too large or even the A-B and B-C pairs would be incompatible.)
Is this a valid way of thinking about the continuity concept? That a “species” is static at local timescales but variable at larger timescales?
* For legal and ick reasons, X is >3.
If I understand your question, then yes. That is, a cross between ancestor A and descendant C might not work if they were separated enough.
It is also possible at times that an individual from one generation is reproductively isolated from the previous generation. A complex chromosomal rearrangement or polyploidy can do that.
While this criterion could be applied over multiple generations for fast-maturing and long-lived species (e.g. cats), or ancestral gametes kept frozen, it really isn’t a relevant criterion for what we usually mean by species (but of course there are already dozens of distinct species concepts in circulation, and you can make up new ones and explore their implications if that’s your interest).
“…if humans now exist but didn’t always exist, then there MUST have been a first human…”
And yet, the video presents clear evidence that this statement is false. I am not even sure it could be regarded as logical, as it is obviously untrue (why not 10 first humans appearing at the same time by advanced alien technology?), but that may be an artefact of how you phrased it combined with my overall ignorance of logic.
Feynman sums it up best: “If it does not agree with experiment, then it is wrong.”
Please see the very simple argument in #23 below, and let me know what’s wrong with it.
Dawkins in _The Ancestors Tale_, I believe it was, suggests that the first human (or first of any other clade) can only be determined *post facto*, as the last common ancestor of a group. “Human” has an ordinary meaning, so this would introduce a technical term, which might not map on in a way that would facilitate understanding. Should it therefore not be used? Dunno, talk to a biologist. 😉
Two things: First, shouldn’t the Dawkins’ work that served as inspiration for the PBS video be The Ancestors Tale? It’s a wonderful treatment of evolutionary history and the role of contingency, highly recommended. I will confess that I was not a big fan of The Magic of Reality and so put it down after a quick skim so perhaps it was rehashed there, as well.
Second, I’ve found it useful in my own mind and in conversations with folks still curious about the “Why are there still monkeys?” question to conduct a quick and easy thought experiment. Draw a brief phylogenetic tree whose root is somewhere in time prior to the human/chimpanzee/bonobo divergence. Point out the obvious fact that we recognize each extant population as distinct species and then draw attention to the node(s) that indicate common ancestry. Simply ask: “Well, if chimps came from this ancestral population, can we think of that common ancestor as a chimp? The answer is superficially “Yes”, but then repeat the exercise for bonobos and humans and it quickly becomes evident to the perhaps naive listener that the common ancestor was neither chimp, bonobo, or human as we now recognize them, but that it was an amalgam of sorts possessing the evolutionary potential to give rise to each of the extant species we see in the present day.
Well, it works for me.
Magic of Reality is intended for children.
Which doesn’t mean it has no value for older readers!
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Agree!
I just got the impression that Scott mightn’t have been aware (comparing it to Ancestor’s Tale).
Climbing Mount Improbable is my favorite of Dawkins’ books.
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Thanks.
As an interested layman, I feel that the video gives me a better understanding (though, naturally, not complete) of a complicated issue.
If you imagine there is a single gene that makes something human, then there could have been a single mutation that originated that gene (from some existing DNA chain), and there would have been a single Homo Erectus individual who had that key gene. So that individual would suddenly not be Homo Erectus anymore but would be the first Homo Sapiens.
You wouldn’t be able to see it in the person’s outward appearance. It would just be in the genes.
I think this is the kind of thinking that gets people confused. You just have to point out that there is no such single gene that makes people human.
I’m afraid this video has problems. First, it adopts the definition of “human = Homo sapiens“, but that’s never how I use the term in evolutionary context, and I don’t think many others do. Rather, “human = Homo“, so Homo erectus is human, by definition. If the video had chosen to use an English vernacular name (as it does for more recent ancestors), Homo erectus would have been “Java man”, or perhaps “Peking man”, and it would be odd to say a “man” was not human. This is just a matter of definition, but it gets the video off on a non-conventional foot.
Second, it calls Hylonomus a “lizard” which it most definitely isn’t. Now if you wanted to call it “lizard-like” or some such, that would be fine. In earlier parts of the video, they are careful to use resemblance terms (e.g., noting that Proconsul looks like an Old World monkey, rather than saying it is an Old World monkey [although to me, being tail-less, it’s more like an ape]).
Most significantly, the video takes first an extremely gradualistic view of evolution, and then contradicts that view, without explaining or noting the jarring contradiction. Now, I’m pretty gradualist myself, but one does not have to be a macromutationist to acknowledge that speciation sometimes adds a distinct inflection point in a chronological lineage, which does make it at least at times quite sensible to speak of the “first” of some lineage. I’m thinking of allopolyploid speciation (formation of a new species by hybridization of two existing species) as a noncontroversial example.
And then, having emphasized that it’s all a smooth road, suddenly life is “stepping stones”, which we call “species”?!? So the whole video is wrong to that point? Or is he claiming life only looks like stepping stones due to imperfection of the fossil record? To me, it seems that he is just straightforwardly contradicting himself, without being aware that he’s doing so. Interpreting the video as ending on a note about the imperfection of the fossil record preserves its coherence, but in a way that will leave most viewers (including me) confused.
I thought the stepping stone illustration seemed directly contradictory to the rest of their message.
>i?Pace my comment to Gregory below, maybe this would have been clearer if Hanson had stuck to the film reel metaphor?
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Perhaps I need to re-watch it. That part seemed to go by particularly fast.
* HTML fail … Pace …
I saw these issues as well. Also, he says that this or that specific species is his direct ancestor, and one should not do that. Those extinct species represent an ancestor only by proxy, since we must assume that we do not find direct ancestors in the fossil record.
An exception can be H. erectus, which is probably a direct ancestor of H. sapiens.
« Or is he claiming life only looks like stepping stones due to imperfection of the fossil record? »
That’s certainly what I thought he was claiming.
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Prof. Mayer, can you recommend any other videos like this on evolution that you have found to be more accurate? As someone who attended a yeshiva high school where the sections on evolution and age of the universe (and sexual reproduction) were removed from our textbooks, I’d love to find more videos like this that dumb things down for those without a good hard science background like me. Even though I’m in my 30s, I tend to learn better from kids’ videos like this than I do from books, for some reason.
To me, the video skips two crucial understandings that make it all easier:
1. Species is an arbitrary term that humans created to make discussions easier; it does not define a distinct separation (which is why ring species is such an interesting concept, if not physically demonstrated,)
2. We refer to older hominids as different species based on the number of anatomical differences, since every other method of defining species cannot be applied, and because we do not have enough fossils to determine exact lineage.
Thus, there is no first human because there is no purpose in defining one as first.
I loved Dawkins’ comparison of the evolution of biological species with the evolution of languages. There was no “first human” any more than there was a “first Spanish speaker”.
I’m sorry, Classical Logic says there must have been. 😉
If there was only one first Spanish speaker, who was she talking to?
Don’t ask me, ask Classical Logic. 😉
See latter part of the discussion at # 12 above.
All this mocking of classical logic reminds me of theists who are happy to use logic to argue for theism — until they run into a problem, at which point they start calling it “merely human logic.”
I should point out that Graham Priest — as nonclassical a logician as there is! — emphasizes that nonclassical logic can’t solve the sorites paradox.
Perhaps that’s true of all known nonclassical logics, but to say for ever? Who knows. Incidentally, there’s a way in which there’s a way out already: simply do not admit vague predicates at all. There’s a tradition of doing this. Russell and Mario Bunge, for example, are both in this tradition. The latter doesn’t care (philosophically) about semantics for ordinary language, so it arguably doesn’t matter. Pick a stipulative definition for science and go. (See above about cladism, for example.)
The sorites paradox attacks even the slightest imprecision. So stipulating precise definitions will work only if we eliminate all of the imprecision, in which case the definitions will be so precise that we can’t use them!
Suppose we stipulate that organisms are conspecific if and only if their genomes are exactly 99% or more alike. First, we won’t be able to tell if two organisms are conspecific without sequencing their genomes! We can’t simply assume that parents and offspring always belong to the same species, because (as I argue in #23 below) that implies infinitely many generations of the same species. Second, any measurements we ever take require rounding for the last digit: they’re never perfectly precise. You may say, “Who cares? They’re precise enough!” But the vague phrase “precise enough” invites the sorites back in.
No — Classical logic says only that there must have been a first Latin speaker and a first Greek speaker …
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Let’s ask Diana–she’ll know who they were.
Assuming that private languages are impossible, it takes at least two speakers for anyone to speak Spanish. But if there was no first group of Spanish-speakers, then there was (of course) no second group, and therefore no third (etc.), and therefore no groups of Spanish-speakers at all. You may scoff, but that doesn’t refute the reasoning; it just sweeps the problem under the rug.
I also like the language analogy. Nearly every person in southern Europe over the past 2000 years spoke the same language as his parents and his children. We cannot pick out the point when Latin became Old French. We cannot name the one first speaker of modern Spanish. Also, even though French, Spanish, Italian and other romance languages come from Latin, no one would ask why isn’t there a crocoduck language with French verbs and Spanish nouns.
We cannot name the one first speaker of modern Spanish.
Right. But nothing in the epistemic theory of vagueness implies that we can — the contrary, in fact. But our inability to name the first group of Spanish-speakers doesn’t imply that there wasn’t a first group. Indeed, if there are now groups of Spanish-speakers but weren’t always groups of Spanish-speakers, then there must have been a first group (or, though it’s unlikely) an exact tie for first among more than one group.
Fine. Pierre in the year 1262 was the first speaker of modern French. Until March 15,1262, he spoke middle French. Prove me wrong.
Sure, lines can be drawn, but they are arbitrary. The lines are based on assumptions and opinions on which factors are most important when distinguishing between two points on a continuum of subtle changes. The continuum exists. Points on the continuum exist. The lines are imaginary human constructs.
Please see my reply to you under #23 below. Nothing in the epistemic theory of vagueness implies that we can know when the sharp transition occurred or where to draw the line. Indeed, that’s the point of the theory: vagueness arises from ignorance. According to the theory, it’s vanishingly unlikely that you’ve picked out the true cutoff when you say “March 15, 1262.”
Unlike the real numbers, human generations aren’t literally “a continuum”: there are adjacent human generations (e.g., me and my children), but there aren’t adjacent real numbers. Talk of continua is misleading here.
There is continuity of cell membranes, direct inheritance of whole organelles from the maternal oocyte, and whole chunks of chromosomes that pass intact from parents to child. Talk of disjunct generations is misleading here.
Naughty Ant
I take it you don’t worry that your tongue will get permanently stuck in your cheek? Or would that be chelicera?
Reblogged this on My Selfish Gene.
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Really, the logical flaw in the video is quite simple. The video claims:
(1) EVERY human that has ever existed is the offspring of human parents who belong to a previous generation.
But a little reflection shows that (1) implies
(2) The number of human generations is INFINITE.
Surely (2) is false. Therefore, (1) is false. Believe me, I’m no creationist! But evolutionary theory has GOT to get by without asserting (1).
I believe you missed the point. Every individual is the child of parents who look a lot like him, and the parent of children who look a lot like him. But two individuals 1,000 or 10,000 or 100,000 generations apart will look very different fryom each other. There is no clear place to draw a line where species one ends and species two begins, despite the plain fact that one and two are different species.
Think about the progression from old English to middle English to modern English. No one could name the last speaker of old English, or the first speaker of modern English. Yet I speak modern English and find old English unintelligible.
Every individual is the child of parents who look a lot like him, and the parent of children who look a lot like him.
The video repeatedly says belong to the same species (i.e., human), not look a lot like. If there’s something wrong with my brief argument in #23, pray tell.
I agree that there’s “no clear place to draw a line” in the sense that we can’t KNOW where the sharp transition occurred. But that doesn’t at all imply that no sharp transition DID occur (especially given that it HAD to occur).
When I was little, my dad would count my fingers – 1 2 3 4 5 on my left hand, 10 9 8 7 6 on my right hand. Then he would add 5 and 6 and “prove” I had 11 fingers. Logic is amazing.
Not sure why I keep thinking about this…..
The flaw in your dad’s reasoning is easy to spot. You haven’t identified a flaw in my #23. Surely your dad’s trick hasn’t made you distrust logic altogether!
So…at what precise time in years, months, days, hours, minutes and seconds did you stop being a child and start being an adolescent.
The following are all true statements:
– You were once a child.
– You were once an adolescent.
– There was a period of time during which is would have been difficult to say whether you were a child or an adolescent.
You were once a child. You were once an adolescent. There was a period of time during which is would have been difficult to say whether you were a child or an adolescent.
All true! But none of them imply that there wasn’t a sharp (if unknowable) transition from one stage to the other.
So at what precise time in years, months, days, hours, minutes and seconds did you stop being a child and start being an adolescent?
I don’t know. Nobody knows. But the sharp transition needn’t be knowable in order for it to exist.
Firstly, I don’t think (1) is ever asserted, and if so it’s a dumb mistake (I don’t care which).
Secondly (and with regard to your distinct assertions about sorites above), semantics is fuzzy and/or multidimensional, and can create syntactic continuities and discontinuities that are different depending on how you look at them. ‘Human’ is a modern English word, and we can trace its Indo-European cognates back for a couple of thousand years (with written evidence) and by comparative and reconstructive methods for between 5 and 10 thousand. Probably none of my ancestors older than that were ever called ‘human’ or a strictly synonymous term. What makes you think the predicate ‘is a human’ can be applied any further than that?
Today we use concepts and labels that are defined by reference to things that exist and can be observed today. As a biologist and palaeontologist I practice taxonomy on specimens that are actually available; a lot of the time we can identify a specimen as belonging to a particular species and (using a lot of detailed and arbitrary and sometimes contradictory rules like the ICZN) attach a name to it, but in some cases (e.g. hybrids, fragmentary remains, or intermediate transitional forms) it may be unhelpful to do so. We can define taxa in a way that (theoretically) includes or excludes certain organisms that may have, or must have existed, but there is nothing there to actually classify unless we can observe it.
Your proof of the First Human strikes me as the kind of logic puzzle Lewis Carroll played with, that turns to bullshit in real life. “‘The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.”
(Sorry Susan, meant to reply to SM)
I’m criticizing the video, so I need to care whether it asserts claim (1). It clearly does assert (1). In fact, (1) follows from the video’s more general claim that parents and their offspring always belong to the same species. If you agree with me that the video’s claims are dumb mistakes, that’s progress!
As for the rest of your comment, I can’t improve on what Timothy Williamson (Oxford) has already written about such reasoning. Like you, I used to believe that the argument for the existence of sharp cutoffs had to be bullshit! But I didn’t know the literature. Much reading and discussion later, I now think the argument has got to be sound. Even Graham Priest — no friend at all of classical logic! — thinks it is.
It seems to me that you’re pontificating on a biological question without referring to biological reality. You insist on presuming that ‘the same species’ means the same thing when applied to individuals/populations at a single time (e.g. parent and offspring, in the statement you rewrite as the claim (1) that was never made in the video) as it does when comparing individuals/populations separated by many thousands of generations. This is not the case in any practical sense. There are dozens of logically distinct species concepts used for different purposes; when used with understanding they don’t create conflict, but species names are post hoc labels, not underlying realities.
As we’ve seen recently, philosophical thinking can be useful in the development of scientific understanding, or it can be irrelevant bullshit. I think this is one of those times.
John –
Bravo
You insist on presuming that ‘the same species’ means the same thing when applied to individuals/populations at a single time (e.g. parent and offspring, in the statement you rewrite as the claim (1) that was never made in the video)…
The video at 2:32: “Every generation is the same species at its parents and the same species as its children.”
How does that claim not imply (as I wrote in #23):
(1) EVERY human that has ever existed is the offspring of human parents who belong to a previous generation.
The video’s claim implies that every member of the human species had parents belonging to the human species. Assuming that no two generations can be each other’s offspring, that implies infinitely many generations of the human species.
Here’s where I think you’re going wrong, Steve: you’re assuming that the “species” in “same species as” refers to some objectively defined set (“the human species”) of which one is either a member or not.
But that’s not what “same species as” means in this context. The whole thrust of the video is that “same species as” is a measure of genetic similarity between pairs of individuals, not a predicate about set membership.
On this view, I am the same species as my father, and he is the same species as his father, and so on back through history, but (and this is the point you seem to be missing) the “species” in question is not a constant. It changes each time we move the cursor back one generation.
So it is not the case that what the video says implies your claim (1). The leap from (pairwise) “same species” to (objectively defined) “human species” is one you made without warrant from anything in the video.
“(1) EVERY human that has ever existed is the offspring of human parents who belong to a previous generation.”
(1)Every day that you were an adolescent was preceded by a day that you were an adolescent
“But a little reflection shows that (1) implies
(2) The number of human generations is INFINITE.”
But a little reflection shows that (1)implies
(2) You have always been an adolescent.
Right! So I deny your (1) about adolescence. I hope you deny it too. Otherwise, not only were you always an adolescent, but you’re also infinitely old! Both versions of (1) are, in John Scanlon’s words, dumb mistakes.
Right, but you lived through your childhood and adolescence, so, if there is a sharp line that separates your childhood from your adolescence, why can’t you tell me when that occurred? Please locate the exact second in time that that occurred.
The fact is that there was a period of several years when you were transitioning from childhood to adolescence and, during this time, it would have been difficult to tell whether you were either a child or an adolescent.
Moreover, during that period of transition, every second that you were in that period of transition was preceded and followed by a second that you were in that period of transition.
Why can’t you tell me when that occurred? Please locate the exact second in time that that occurred.
You seem to think that I should be able to know every fact about myself, with limitless precision. What was your exact weight to the nearest pound at 12:00 noon (your local time) one year ago today? Even if you don’t know, there’s a correct answer.
Moreover, during that period of transition, every second that you were in that period of transition was preceded and followed by a second that you were in that period of transition.
Re-read what you wrote: If it’s true, then I always have been in that period of transition (going back eons) and always will be (going forward eons). Am I transitioning into adolescence even now? I’d hoped I’d left it behind long ago.
Here’s the last paragraph of my response to the discussion in #12. I go into more detail up there, but this really brings it on home:
The features of any system of logic are not metaphysical principles. I quench my thirst on Aristotle’s tears.
BTW, thanks for the tip about Wiliamson, I’ll go read him now and see if I have reasons to give up embracing vagueness.
I’m glad you intend to read Williamson. I think he’ll persuade you that the vagueness you say you embrace — ontological vagueness, and not just epistemic vagueness arising from our ignorance — is logically incoherent and therefore not even possibly correct. I used to be where you now are! Extensive reading and discussion talked me out of it.
Logic is an extremely useful tool, but it is not reality. When your logic tells you that something “HAD to” have happened, that may be a strong indication that it did, or it could mean there is something wrong with your logic or how you are applying it.
I think the problem here is that species are largely arbitrary groupings made up by us. The truth is that each organism is different from any other (some exceptions, at least in the short term). The differences between two organisms directly related to each other and separated by one generation, parent and child, and the differences between organisms from different orders separated by tens of millions of years, are of the same types of differences. The only variable is the amount of those same types of differences that have accumulated.
It may, in a sense, be more accurate to say that every organism is its own species, but that is fairly useless though very specific. Actual species concepts that are useful are much less specific than that. That lack of specificity is why your logic doesn’t work. Your logical model that is telling you that there “MUST” be a sharp transition between species may be trivially true when applied at a certain scale, but at that scale it is fairly useless and uninteresting.
Bingo.
My Neanderthal genes feels a bit left out.
I agree that while this video is simple, there’s not enough time spent on adaptations that slowly lead to speciation. Creationists don’t seem to understand adaptations. Even in Richard Dawkins explanation from The Magic of Reality, he states, for example, that Homo erectus parents always give birth to Homo erectus children, but neglected to mention children with slowly evolving adaptations. That’s the ticket to grasping evolution through natural selection that others refuse to comprehend or willfully ignore. We need to unite on driving that point home and pounding it in their mind poisoned, thick skulls!
Do you really want to say that your child is slowly evolving? I would say that it would not even have entered Richard Dawkins’ mind to say that, let alone make the mistake of saying so.
The Magic of Reality is not just a children’s book. It a must read for all naysayers of evolution. In just a few pages it clears up misconceptions that people have about evolution. After they are done reading this I would also recommend another must read book written by a professor of evolutionary biology living in Chicago.
There’s a YouTube video (at ForaTV, I think) where Dawkins speaks on the same topic and elaborates the same themes. It’s about 3.40 long.
The video could be understood by a naive person to say that individuals evolve. Populations evolve and speciate. Individuals do not ordinarily do so. There are, of course, exceptions such as polyploid speciation.
Named species represent our best effort to recognize real discrete populations in nature. We recognize species, we do not create them. We do create higher categories, in an effort to communicate our best understanding of phylogenies.
My work has been in fish taxonomy, systematics and phylogeny, so I see nature through that lens.
Reply to Gregory Kusnick (August 26, 2014 at 3:28 pm):
Gregory, you wrote:
But that’s not what “same species as” means in this context. The whole thrust of the video is that “same species as” is a measure of genetic similarity between pairs of individuals, not a predicate about set membership.
Defining species in terms of genetic similarity won’t eliminate sharp cutoffs. If such a definition works, then any two organisms either have enough genetic similarity to count as members of the same species, or they don’t. (It makes no sense to say that they neither do nor don’t, or that they both do and don’t!)
So for any degree of similarity I name (90%, 99%, 99.1%, 99.11%, etc.), either that degree of similarity will be enough for conspecificity, or it won’t — regardless of whether we can know what the precise minimum degree of similarity is.
If we’re stuck with sharp cutoffs anyway, why not a sharp cutoff between human and prehuman — i.e., a human born to nonhuman parents?
I think you’re still missing the point that “same species as” is a pairwise operator, not a unary predicate.
Yes, we can convert it to a unary predicate of the form “member of the same species as person P to within tolerance T“, for arbitrarily chosen values of P and T. In that case your point is trivially true: there must have been some individual (or set of identical twins) who first satisfied that predicate with those parameters.
But so what? By arbitrarily parametrizing the predicate to produce a definite outcome (which in any case we can never actually know), we’ve robbed it of any scientific interest or pedagogical value.
Meanwhile, it remains true (and interesting!) that an unbroken chain of pairwise “same species” relations, with no sharp transitions, can add up to a “not same species” relation between the endpoints of that chain. This central lesson of evolutionary theory is the point of the video, and I don’t see why you’re trying so hard to deny it.
No. My reply explicitly treated conspecificity as a relation, not as a one-place predicate. If we define the relation, as you suggested, by degree of genetic similarity, then we’re still forced to recognize the existence of sharp cutoffs,even if their location is unknowable. I don’t see why you can’t grasp that.
We seem to be talking past each other. I’ll try one more time and then I’m done.
Correct me if I’m wrong, but the point you’re making can be expressed something like this:
(1) Given a sufficiently precise species concept C that yields a definite answer in all cases, and a lineage L of parent-child relationships stretching back sufficiently far, there must be some definite member of L who first satisfies C with respect to the endpoint of L.
OK so far?
The point the video and your opponents here are making is that any plausible species concept must meet two criteria:
(2a) that members of lineage L separated by very small intervals of time (e.g. one generation) are deemed the same species (with a few clear exceptions such as chromosome doubling and hybridization), and
(2b) that members of L separated by very large intervals (e.g. millions of years) are deemed different species.
You seem to be arguing that the truth of proposition (1) (which I don’t dispute) somehow entails that criteria (2a) and (2b) are incompatible, i.e. that if (2b) is satisfied, there must be a discontinuity in L where (2a) fails. This argument doesn’t hold water, and that’s why you’re getting pushback on it.
If that’s not what you’re saying, and you’re just repeatedly asserting proposition (1), then there’s nothing to argue about, since (1) is self-evidently true, and (in my opinion) completely irrelevant to the point of the video.
Sorry: meant to hit “Reply.” See #30, below.
Thanks for your reply. We agree on (1).
My very first comment, #12 above, brought up the sorites paradox, whose point is to challenge the compatibility of claims such as your (2a) and (2b). Yes, we routinely say that (i) adjacent items in a series belong to the same category, while (ii) widely separated items in the series belong to different categories. The problem is that (i) and (ii) are incompatible given classical logic and the principle of bivalence, which says that every proposition (note: not every sentence) is either true or false.
Many people therefore respond by rejecting classical logic and/or bivalence, as I myself once did. I then discovered what the experts have known for a while: rejecting classical logic doesn’t solve the problem (sharp cutoffs remain), and rejecting bivalence for propositions makes no sense and leads to problems as bad as the sorites itself.
As Graham Priest says, “The sorites phenomenon … arises simply because we are forced to recognize the existence of cut-off points where both common sense and philosophical intuition scream that there are none. Thus, the only thing left for a solution to do is to explain why we find the existence of a cut-off so counter-intuitive.”
In short, the sorites is a serious, unsolved problem. The video that Jerry recommended shows how relevant the problem is for biologists! Biologists should want to avoid saying logically inconsistent things, so the sorites is their problem too. The only solution that offers any hope, as far as I can see, is to accept the existence of (perhaps unknowable) sharp cutoffs, such as human offspring of nonhuman parents.
Last try for me as well:
Look at this colour gradient.
http://en.wikipedia.org/wiki/File:Color_gradient_illustrating_a_sorites_paradox.png
Then deny the following:
The colour on the left is green.
The colour on the right is red.
In the middle, and scanning from left to right, green gradually transitions into red.
If you deny that there is a transition zone, then show me the exact point where green becomes red.
Note:
You will need to click on that pictogram to see the colour gradient
I haven’t ever denied, and wouldn’t ever deny, that there is a transition zone, meaning a zone in which it’s not clear how we should label the color or a zone in which we don’t know that color to call it. But that’s compatible with there being a sharp cutoff between (e.g.) green and yellow. Surely we don’t have to know every fact there is, with limitless precision! (Recall my question about your exact weight a year ago.) Our color-distinguishing faculty needn’t be perfectly acute in order for it to have conferred an evolutionary advantage. Please stop inferring “It doesn’t exist” from “We don’t know precisely where it is.”
(BTW, do you admit the mistake I pointed out in my reply to you on August 26, 2014 at 4:48 pm?)
« I haven’t ever denied, and wouldn’t ever deny, that there is a transition zone, meaning a zone in which it’s not clear how we should label the color or a zone in which we don’t know that color to call it. But that’s compatible with there being a sharp cutoff between (e.g.) green and yellow. »
I’m sorry, I just don’t see how that is compatible.
Surely, to say that there is a transition zone between green and yellow implies that there is *no* sharp cutoff? Only that we go through a range of hues that are increasingly “less like green” and “more like yellow”, in however many steps you want; e.g., δλ = 1nm (if we can define λ “green” and “yellow” with some arbitrary degree of precision).
The whole sorites paradox seems to be addressed by using fuzzy logic like this.
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Surely, to say that there is a transition zone between green and yellow implies that there is *no* sharp cutoff?
No, it doesn’t, not in either of the ways I defined “transition zone.” It implies only that the cutoff occurs somewhere in the zone, even if we can’t know precisely where in the zone it occurs. I’ve been asking folks to stop invalidly inferring “A sharp cutoff doesn’t exist” from “We don’t know where it is” — especially when logic proves that a sharp cutoff MUST exist.
Importantly, fuzzy logic doesn’t eliminate all the sharp cutoffs. If the left end of the gradient is green to degree 1, and the right end isn’t green to degree 1, then (going left to right) there must be a first color that’s not green to degree 1, i.e., a sharp transition from degree 1 to some degree less than 1. We’re stuck with sharp transitions! So why not a sharp transition between (say) green and yellow?
Then I think you’re being anti-scientific, Steve, preferring what logic *proves* over what we see empirically. (I’m not sure if calling you a *philosophist* infringes the roolz… )
Classically, we can make the transition steps arbitrarily small, so any transition is continuous and smooth rather than sharp. Even if we take account of quantum effects (stepwise transitions), they are of the order of the Planck length, something like 1/10,000,000,000,000,000,000,000,000,000 the wavelength of green or yellow light. Still a continuous and smooth transition as far as our eyes are concerned.
So, there’s no sharp transition between green and yellow, just nonillions of tiny all-but-continuous transitions, and fuzzy (multivalued) boundaries (dependent on visual acuity, psychology, culture and language) between what people call green and what they call “slightly” yellowish green &c.
Actually, it may be more to the point that there *isn’t* a sharp boundary to what we call “green” — or what we call a “species” (as Gregory was arguing) — which thus precludes any sharp transitions.
Even without going back in time, the fuzzy boundaries between species are very evident. For a long time, the domestic dog was /Canis familiaris/, a species in its own right; now it’s regarded as a subspecies of grey wolf, /Canis lupus familiaris/. Conversely, some subspecies of giraffe (for ex.) are now recognised as distinct species. (As Gregory noted, and Jerry has discussed many times in the past, there are different definitions of species which are useful in different contexts.)
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PS. Cerulean might have been a good colour example to work with. I’ll leave it to Diana to provide the “classical” definition that exemplifies the fuzziness.
You appealed again to fuzzy (multivalued) semantics while simply ignoring the objection I raised against it! Assign colors degrees of greenness on a continuous scale of 0 to 1. Presumably, “true green” gets the value 1, and “true red” gets some value less than 1. As you move from true green toward yellow, you can’t keep assigning 1; eventually you have to assign some value less than 1 — suddenly, i.e., sharply. This is called the “forced march sorites,” and it’s well-known to philosophers.
The rest of your comment trades between (a) what’s truly continuous and (b) what’s continuous “as far as our eyes are concerned.” If (a) and (b) were the same, no one would watch movies. If you refuse to recognize such basic distinctions, I see no point in continuing our conversation.
No, per my reply elsewhere, the species case is exactly analogous to (b).
“True” green is a not a single-valued thing: G ± σ(ψ) — i.e., the spread is dependent on the observer’s psychology &c. As long a δ ≪ σ the new hue is still “green”.
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OK, one last reply (really).
Sorites is a problem only if you insist on interpreting “same species” as membership in a category. But as I’ve tried to point out, that’s not the right interpretation. “Same species” is a relation between pairs of individuals.
Consider the natural numbers. We can define a relation R to be “differs by one from”. It’s now clear that 1 R 2, 2 R 3, 3 R 4, and so on, but it is not the case that 1 R 1,000,000. I hope you can agree there there’s no paradox here, that R is well-defined, and that there is no discontinuity where R fails on consecutive numbers.
Returning to biology, let’s define S to mean, roughly, “similar enough to breed with”. This is the “same species” relation we’re talking about, and it applies to the consecutive members of lineage L just as R does to the natural numbers. So L1 S L2, L2 S L3, and so on, but it is not the case that L1 S L1,000,000. Again, no paradox and no discontinuity.
So when we identify a population as a species, we’re not saying that there’s some well-defined category that they all belong to. Categories, as you’ve made clear, are the wrong tool for this job. What we mean by “species” is a web of S-like relationships that connect members of a population to each other, but not to members of other populations. We observe that, in nature, such webs tend to form disconnected clusters, and those clusters are what we call species.
Unfortunately, your analogy doesn’t work. If R is “differs by one from,” then although it’s true that 1 R 2 and 2 R 3, it’s false that 1 R 3. So there is discontinuity: for any integer n, there’s a unique first m for which which n R m fails. We even know what it is: n+2 (ascending), n-2 (descending).
Furthermore, if your analogy worked, then no organism could breed with its grandson or granddaughter. But we know that can happen. So you need to allow L1 S L3 while disallowing L1 S Ln for some n. That’s exactly the sorites situation, so the sorites does make trouble for your proposal.
No analogies are perfect. They aren’t meant to be. They are meant to serve the purpose of explaining something. You abuse analogies by dissecting them.
For example, the colour gradation clearly shows that there is not even any sharp line where the colour immediately to the left looks any different to the colour to the right, let alone a line where green becomes red.
You got out of having to identify the moment when you stopped being a child and started being an adolescent but saying that you cannot remember the details of your life sufficiently to identify this moment. I thought this was rather disengenuous because that would imply that you would have recognised that moment when you actually went through it but just can’t remember now when exactly that was.
Anyway, I decided to let that pass and give you an example that you CAN actually observe…that colour gradation. This time your explanation was different. The colour gradation is analogous to your timeline, yet your explanation for why they are wrong is different.
The numbers you quote make no difference to my colour gradation analogy. There clearly is green at the left and red on the right, but there is no vertical line on the grid where there is green immediately to the left and red immediately to the right. Period.
Otherwise draw me that line.
BillyJoe: My reply was to Gregory Kusnick’s comment immediately above. It was his analogy (involving the natural numbers) that I was criticizing. I think you mistook my reply to him as a reply to you.
Sorry, that didn’t work. Try Again…
Fine, but I’m still waiting for you to draw that vertical line on the colour gradation chart that divides green on the left and red on the right.
There is obviously no such line otherwise you would have drawn it by now.
It is a fact that for every vertical line on that colour gradation chart, the colour immediately to the left is indistinguishable from the colour immediately to the right. Yet at far left we have green and at far right we have red.
Analogously for species.
Sorry: my reply appears as #31 above.
Sorry: somehow my reply appears as #31 above.
Somehow my post #33 appears after my post #32, though clearly I posted #33 before #32.
Perhaps your quaint “logic” has bamboozled even the program.
1. The line you say you want drawn wouldn’t divide green from red (alone). It would divide green from the first non-green color going left to right, i.e., yellow if we’re using the coarsest labels.
2. As I’ve repeatedly emphasized, the epistemic theory of vagueness says we can’t know the location of the sharp cutoffs that nevertheless must exist. That’s the whole point: vagueness arises from our ignorance of the location of sharp cutoffs. You’re asking me to draw a line whose location the theory says I can’t know with arbitrary precision. That’s an unfair demand.
3. In math, non-constructive proofs (often called “existence proofs”) are common: we show that solutions must exist even if we can’t identify any particular solution. That’s what’s going on here: there’s an airtight proof that sharp cutoffs must exist, and the proof doesn’t rely on identifying any of those cutoffs. (As I and others have said, abandoning classical logic or bivalent semantics won’t help.)
4. “It is a fact that for every vertical line on that colour gradation chart, the colour immediately to the left is indistinguishable from the colour immediately to the right.” I agree, as long as “indistinguishable” means “we can’t tell the difference” and not “there is no difference, not even one we can’t detect.”
« 4. “It is a fact that for every vertical line on that colour gradation chart, the colour immediately to the left is indistinguishable from the colour immediately to the right.” I agree, as long as “indistinguishable” means “we /can’t tell/ the difference” and not “there /is no/ difference, not even one we can’t detect.” »
But that’s exactly what we mean when we’re discussing species. We’re not concerned with differences between generations at the genetic level (which we *can* actually detect); we’re saying that we can’t tell generations apart in terms of behavior, vocalizations, morphology, the ability to produce viable offspring with each other, and so on.
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Whoa. So all you folks have been saying is this?
(A) Individual differences in behavior, vocalizations, morphology, the ability to produce viable offspring with each other, etc., can be too small for us to detect and yet, over time, can add up to differences that ARE large enough for us to detect.
If all you’ve been saying is A, then no sane person could disagree with you.
But in fact a number of folks here have repeatedly said something different:
(B) Sharp cutoffs between species don’t exist — “period,” as some here have written — not even cutoffs that are undetectable by us.
I’ve been denying B. If you don’t assert B after all, then I have no quarrel with you.
“The line…would divide green from the first non-green color going left to right…”
No. Each and every vertical line that you might draw on the colour gradation chart would have colours immediately to the left and right that are totally indistinguishable from each other.
“I agree, as long as “indistinguishable” means “we can’t tell the difference” and not “there is no difference, not even one we can’t detect.””
The difference is infinitesmal. That is the point. With infinitesmally small gradations you can get from green to red without any sharp cut off anywhere. They are all infinitesmally small changes.
If green and red are species…well, I hope you get the point finally.
“the epistemic theory of vagueness says we can’t know the location of the sharp cutoffs that nevertheless must exist”
We can put the vertical line* anywhere and everywhere and, on each occasion that we do so, we find that the difference between the colour immediately to the right of that line and the colour immediately to the left of that line is infinitesmally small. This proves that there is no sharp cutoff whatever your epistemic theory of vagueness may say.
*remember that a line has no width
The difference is infinitesmal. That is the point. With infinitesmally small gradations you can get from green to red without any sharp cut off anywhere. They are all infinitesmally small changes.
I honestly don’t see how these sentences reply to the statement of mine to which you were replying. You don’t say what you mean by “infinitesimal,” so I’m guessing that you mean too small for us to detect. (The strict definition of “infinitesimal” is “nonzero but smaller than any positive real number,” which is a bizarre concept.)
If that’s what you mean by “infinitesimal,” then your claim is a version of the claim I labeled “A” in my latest response to Ant. No sane person denies that claim. I never have.
But from the fact that a change is too small for us to detect, it doesn’t follow that the change doesn’t exist. Furthermore, we have an airtight classical proof that the change must exist even if we can’t detect it.
Of course the change exists. The point is that the change is gradual – meaning that there is no sharp cut-off.
It seems bizzarre to me that you want say that both are true. I mean, it’s either one or the other. Either there’s a gradual change or a sharp cut-off. It cannot be both.
It’s bizarre to me that you won’t allow that the change from green to non-green can look gradual without in fact being gradual. Do you think that a movie can’t look continuous without in fact being continuous? Can’t there ever be a discrepancy between the way things appear to us and the way they really are?
It’s also bizarre to me that you asserted claims (August 26, 2014 at 2:07 pm) that imply that I’m infinitely old and never retracted those claims after I pointed out the implication (August 26, 2014 at 4:48 pm).
The implication that you are infinitely old is just a conclusion based on your faulty reasoning. I have indirectly replied to it several times in my follow up posts. For example…
The colour gradation strip shows clearly that your implication is wrong. We can get from green to red gradually without any evidence of a sharp cut-off, and without taking an infinity to get there.
But now you’ve compounded your error by making “gradual” mean the same as “continuous”. Superman can get to the top of a building in one continuous leap. We can get there gradually – one step at a time.
And you have yet to show me where that elusive sharp cut-off(one big leap) is between green and red (green on one side and red on the other side). On the other hand, I have clearly and conclusively demonstrated that the change is gradual (numerous small steps).
Reply to Ant (August 28, 2014 at 9:50 am):
No, per my reply elsewhere, the species case is exactly analogous to (b).
Ah, so further confirmation that, as far as you’re concerned, two organisms belong to different species only if we can tell that they do. That’s what an exact analogy to (b) implies. A movie looks continuous to us even if it’s in fact composed of discrete still images. You’re saying that if the transition looks continuous to us, then the transition is in fact continuous, i.e., it lacks any sharp cutoffs.
Again, no sane person denies that cutoffs can be too small for us to detect. But the cutoffs can nonetheless exist, especially when we have a proof that they do.
@BillyJoe (August 29, 2014 at 10:23 pm):
The implication that you are infinitely old is just a conclusion based on your faulty reasoning.
If you recognize nothing else, at least recognize that mistake. You wrote (August 26, 2014 at 2:07 pm):
Moreover, during that period of transition, every second that you were in that period of transition was preceded and followed by a second that you were in that period of transition.
I teach logic at university. I would expect any of my first-year students to see that your statement implies that I’m infinitely old. Take any period in my life (a period of transition, or whatever). If every second that I’m in that period is preceded by a second during which I’m in that period, then I’m infinitely many seconds old. Moreover, if every second that I’m in that period is followed by a second during which I’m in that period, I will exist forever. (A second is a nonzero unit of time; it’s not an instant.)
Your repeated failure to see those obvious implications makes your general sloppiness in argumentation less surprising, I suppose.
In your latest comment, you treat “gradual” (i.e., lacking sharp cutoffs) as equivalent to “numerous small steps.” Here’s why that reasoning fails. Count, by 1, upward from negative 1 million. The transition from negative to non-negative numbers will take numerous small steps, but it won’t be gradual: there’s a sharp cutoff, at 0, where the numbers suddenly become non-negative. (Here we can identify the cutoff, but there’s no reason to think we’ll be able to for every transition.)
You repeatedly asked me to draw you a line that I’ve admitted I can’t draw and that the theory I’m defending says none of us can draw. I don’t know if I can continue to converse with someone who reasons that poorly.
Okay, last reply.
If, according to the “epistemic vagueness theory” yopu mentioned, it is not possible to identify a cut-off in a colour gradation strip that is right before your eyes, then I would have to question the validity of that theory. You had an excuse with not being able to identify the moment that your stopped being a child and started being an adolescent, but you have no excuse for not being to identify the sharp cut-off from green to red in a colour gradation strip that is right before your eyes. In fact, there is clearly no line that you could possibly draw that separates green on the left from red on the right.
Similarly, there is no sharp cut-off between species. As life evolves, there is no sharp cut-off from one generation to the next, where one species stops and another species begins. But, if you stand back and examine the evolutionary record, you will be able to identify separate species. In the colour gradation strip, as you move the vertical line from left to right there is no sharp cut-off where green becomes red. But if you look at the whole strip, there is clearly green on the left and red on the right. As you moved through your life, there was no sharp cut-off where childhood stopped and adolescence began. Yet, clearly, you were once a child and, at some later stage of your life, you were an adolescent.
“I teach logic at university…Take any period in my life…If every second that I’m in that period is preceded by a second during which I’m in that period, then I’m infinitely many seconds old”
Your logic is strangling you. You are failing to distinguish between two different ways of looking at things. The first is you travelling through life. In that way of looking at things, it is never possible to say that one second ago your were a child and now you are an adolescent. The second way of looking at things is where you stand back and look at your life’s trajectory. If you turn to that way of looking at things, you can clearly identify periods of time when you were a child and periods of time when you were an adolescent – and a period of transition. The two are not mutually exclusive, no matter what your “logic” tells you.
“Count, by 1, upward from negative 1 million. The transition from negative to non-negative numbers will take numerous small steps, but it won’t be gradual: there’s a sharp cutoff, at 0, where the numbers suddenly become non-negative”
Congratulations! You have identified a sharp cut-off (see note below)! Now please identify the sharp cut-off in the colour gradation strip! Otherwise please acknowledge that there is none.
NOTE: Of course I have never denied that sharp cut-offs exist, just that they don’t exist in the situations we have been discussing: one species to another species; childhood to adolescence; green to red. Clearly you can die before reaching adolescence, the paper might have run out before green became red; dinosaur can and did become extinct.
Last reply to anyone who, at this stage of the discussion, would write what you just did: it’s a pity that no one managed to teach you how to reason before it became too late. If you represent the average adult in our society, I weep for humanity.
Pardon me for jumping back in, but you’re out of line here, Steve. Please reread Da Roolz, particularly Roolz 7 (no personal insults) and 8 (don’t dominate threads with unproductive disagreements).
Mr. Maitzen, you’re not only dominating the thread, but as has been pointed out, you’ve violated the rules by insulting fellow readers. I expect you to apologize for what you just said above, which is extremely rude, and apologize without qualification. If you don’t, you will never post here again.
You may be a professor and all, but you haven’t mastered how to engage in civil discourse on the internet.
Now apologize, please. What a rude thing you said!
I have no desire to post here or follow your site any longer. The intellectual caliber of the comments is shameful and depressing.
I’m SO glad you were able to overcome your reticence post here to give us one last chance to bask one last time in your superior intellect. Usually people with your combination of brilliance and self-image of superiority just go away without giving us a final word. Thank you, and I hope you find a website that is truly appreciative of your brainpower.
So there – LOL
« I have no desire to post here … [t]he intellectual caliber of the comments is shameful and depressing. »
Um, whose … ? 😝
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Reblogged this on Living life to the limit.