- Affirming the Consequent is a logical fallacy that takes a known true statement [if P then Q] and invalidly concludes its converse [if Q then P]:
- If Bill Gates owns Fort Knox, then Bill Gates is rich. Bill Gates is rich. Therefore, Bill Gates owns Fort Knox. False!
- If an animal is a dog, then it has four legs. My cat has four legs. Therefore, my cat is a dog. False!
- If it’s raining, then the streets are wet. The streets are wet. Therefore it’s raining. False! It could be raining or it could be something else. The “therefore” claim is false.
- How does ‘Affirming the consequent’ apply to evolution? We have not observed “evolution”. No one has, and no one will, despite the effort (see LTEE). What was observed is Resemblance, the Birth Mechanism, Variability and Adaptability. Neither of these (even combined) can logically be extrapolated to “evolution”, namely the hypothesized transmutation of one type of organism into another. Proofs of “evolution” always take the form: If “evolution” is true, then XYZ is true. XYZ is true. Therefore “evolution” is true. This is a classical Affirming the Consequent logical fallacy.
- Let’s see some concrete examples of “proof of evolution” fallacies:
- If “evolution” is true, some fossils are ancestors of and therefore resemble existing organisms. Fossils resemble one another and existing organisms. Therefore “evolution” is true. This argument fails because there will always be some resemblance between two or more entities (even chairs and cats have four legs in general). Also, a fossil can always be from an unrelated branch of the “tree of life” which circularly presupposes “evolution” anyway.
- If “evolution” is true, organisms are genetically similar. Organisms are genetically similar. Therefore “evolution” is true. This argument is false because other hypotheses such as common design account for genetic similarities just as well.
- If “evolution” is true, one might expect common embryology. Similar organisms have similar embryology. Therefore “evolution” is true. This fails because embryology is expected to match genetics and morphology, hence the previous counterargument applies.
- If “evolution” is true, one might expect vestigial organs. What looks like vestigial organs can be observed. Therefore “evolution” is true. This fails because what if those organs are useful rather that “vestigial”? And why would “evolution” not do away with “vestigial” organs as soon as they become useless? In sum, why can’t these organs have another reason or origin than “evolution”?
- If “evolution” is true, one expects adaptability such as antibiotic resistance. Antibiotic resistance is observed. Therefore “evolution” is true. This fails because adaptabilities such as antibiotic resistance are compatible with other hypotheses, not just “evolution”. In addition, antibiotic resistance is ubiquitous, limited, reversible, and never observed to result in organism transmutation aka “evolution”.
- How can “proofs of evolution” avoid the ‘Affirming the Consequent’ logical fallacy? Direct confirmation of “evolution” is unlikely as shown by the LTEE study. Alternatively, an observation that is true for “evolution” and only for “evolution” might also work. In other words, what’s missing from all the examples above is a true statement of the kind: “only if evolution is true, then XYZ”. Of course, excluding all alternatives to “evolution” is an impossible task therefore, given that Intelligent Design is the main rival, proponents of “evolution” need only add a true statement of the kind: “if Intelligent Design is true, then XYZ is not true” to turn their invalid arguments into valid ones. But even this lower bar cannot be met by “evolution” proponents, thus making all “proofs of evolution” invalid.
- Isn’t then all science ‘Affirming the Consequent’? For example, “if Newtonian physics is true, a ball thrown at angle Theta and speed V will land D meters away. The experiment is carried out, and we find that the ball landed distance D away. Therefor physics is true.” No! This is not a fallacy because it meets the “if and only if” requirement and is limited to “everything else equal” cases. Rockets do not disprove this claim because everything else is not equal between them and thrown inactive projectiles. In addition, no one claims a single experiment confirms all Newtonian Mechanics the way “proofs of evolution” are presented. In this case, multiple combinations of Angles and Speed result in the same Distance without violating Newtonian Mechanics because this experiment proves only portions of the theory.
Links:
https://en.wikipedia.org/wiki/Affirming_the_consequent
https://www.amazon.com/Biblical-Wisdom-Literature-Joseph-Koterski/dp/1598035258
That’s what he has been telling us, and he has been wrong. He has managed to find examples of random people on the internet engaging in invalid propostional statements purported to be in in support of evolutionary biology, but since evolutionary biology does not in fact rest on such propositional statements, he’s been barking up the wrong tree.
What he should have been doing is explain to these people that they are misrepresenting the science of evolutionary biology, instead of taking these people as making authoritative statements on behalf of the field and trying to disprove the science in that way.
All he has accomplished is to find people who are bad at explaining the science of evolutionary biology, and how scientific inference works.
No, for reasons already explained that is not correct. Evolution is based on logic, it’s just that it isn’t based on the kinds of premises Nonlin has found examples of people stating.
Some people are bad at posing their arguments in strictly valid terms. That’s a problem with their ability to properly state the arguments for evolution, not a problem with the science itself.
See what I mean? Grrr grrr grrr, phoodoo vs the world. No, I wasn’t snarling, I was smiling at the familiar pattern.
Well thanks, but as I said, it’s all on the first pages of books you won’t look at. Affirming the consequent is a fallacy of propositional logic.
The syllogism you posted about birds is not reproducible in propositional logic. So, if you’re saying that nonlin is full of shit, I agree and you should have said that a long time back instead of pretending to agree with him in his many errors.
I think, though, that the actual truth is that you still have no idea what the hell you’re talking about.
phoodoo, as you now agree that nonlin is full of shit, you should take a look at his OP on gradualism. Ton of howlers in there too. The guy is almost unlimited fun.
All your biases are belong to us, Neil!
walto,
If Walto can’t understand something, then he posts bullshit .
Walto can’t understand something.
But the good news is he thinks it is in a book somewhere that he can’t find!
You even have Rumraket telling you you are wrong, that has to sting. And you have Jock telling himself, you are wrong. Ouch!
Nonlin was right from the start, evolutionists don’t understand arguments. I guess that is why he has got you all in such a tizzy.
1. If filibuster, not soon Aquarius in time reflex without frankly.
or
2. If not fillibuster not not soon, not Aquarius, out of time, not reflex possibly with not frankly.
Remember premises can be nonsense Walto? That was on page one right? Did you find your book?
No, for reasons already explained he was wrong from the start, Nonlin has merely found examples of random internet nobodies badly stating how scientific reasoning works while arguing for evolution.
In a shocking turn of events, the only people who understand logic are the people with whom phoodoo agrees! 😀
Has he even done that? The various examples in the OP are unattributed, and unless everyone puts scare-quotes round “evolution”, are likely poor paraphrases of imagined arguments.
Allan Miller,
I agree. While I am sure there are many examples of people phrasing arguments poorly on the internet, it strikes me as sufficient that nonlin read a few examples of people talking about applying a Bayesian inference and misinterpreted it as a deductive fallacy.
nonlin’s supposed conclusion
looks like a particularly poor paraphrase.
As keiths noted a while back:
Indeed.
Propositions must be true or false. If you’re saying that one can assign truth values to “Filibuster” and the other one, i’ll be happy to tell you whether your forms are valid or not: it’s childsplay. Sadly, you will have no idea what i mean by “valid.”
And if you’d really like me to post material from the front of intro to logic texts, i’ll be happy to oblige there too. But as it just confirms what everybody has been saying to you and your buddy through hundreds of comments…are you really sure you want me to?
Just confirm the assignability of truth values to your apparently nonsensical statements and your desire to be further embarrassed and I will be happy to comply.
How about some introductory linguistics?
P1. Colorless green ideas sleep furiously
P2. X is a colorless green idea
Hence, X sleeps furiously.
So perhaps semantic nonsense can still take the form of a valid argument (perhaps).
But starting from the grammatical nonsense of “Furiously sleep ideas green colorless”, I don’t see how one can get a valid argument, assuming that words are used according to English grammar. Phoodoo’s stuff seems to fall into the grammatical nonsense category.
But I am happy to be corrected on the above. I just thought you might want a change of pace.
Of course, bringing up quantum nonsense would be to go way off topic.
You also seem to mean something different by “valid” than what Walto has been talking about. He’s taking validity to mean “an argument where the conclusion follows from it’s premises” which is independent of whether the premises are true or even if they make any sense at all
Again,
P
Q
Therefore, R
is not a valid argument form of propositional logic.
BruceS,
So long as we’re defining validity solely in syntactical terms, it doesn’t matter whether the propositions have a sense or are sheer nonsense.
If we’re trying to think about material inference (see here) then yes, semantics does matter to assessing the goodness of inference. But in formal or logical inference, it doesn’t.
The fact that logical validity has nothing to do with semantics, it must be pointed out, is central to the long-standing criticism of symbolic AI (see here. John Searle’s version of the criticism — the Chinese room thought-experiment — is the best-known, though he was ripping off much better arguments by Hubert Dreyfus and by John Haugeland.
dazz,
The argument Bruce gives there depends understanding the relation between terms like “all” and “some” . Validity of those types can be proven with Venn Diagrams.
But in any type of logic, ‘valid’ means that if the premises are true, the conclusion must be true.
Thanks Walto (and apologies to Bruce)
I’ll reread that to see what I’m missing
ETA: I’m guessing you mean that “Colorless green ideas sleep furiously” could be “ALL Colorless green ideas sleep furiously” or “SOME Colorless green ideas sleep furiously”
If the former, the argument is valid, otherwise not. Hope I’m not missing something obvious again, ugh!
dazz,
That’d be right so long as “colorless green ideas” and “sleep furiously” aren’t necessarily devoid of sense (as I guess Chomsky insisted). That is, just as one can wonder if the purported propositions can be true or false in propositional logic, one can wonder whether the predicates can make sense in predicate logic. If the things that are supposed to be assigned truth values or the things that are supposed to hold or fail to hold of terms can’t do so, then you can’t have validity.
Kantian Naturalist,
As can be seen from my last couple of posts, that isn’t quite how i’d put this.
Fair enough. I’m sure there are some subtle problems with identifying deductive inference with syntax — though I’ve long been struck by Wittgenstein’s claim (in the Tractatus) that any deductively valid proof can be written as a tautologous sentence. I don’t know if that’s still a widely held view or not — logic is not my area.
Thanks again, Walto.
What about a generic argument like
If P then Q
P
Therefore Q
Isn’t it impossible to assign truth values to P and Q based on their meaning (or lack thereof)?
dazz,
The letters just have to represent propositions. If they do, that form is valid.
Makes sense 👍
I meant P1 to be taken as: “if anything is a colorless green idea, then that thing sleeps furiously”. Which I guess shows you that even correct English grammar is not enough; the argument has to be clear to someone with a normal grasp of English grammar.
ETA: I see Dazz makes the same point.
I don’t think the fact that the set of colorless green ideas ie empty affects the validity of the argument as phrased above. But then again, you’re the guy with the PhD.
Of course, what it may really mean is that Chomsky was wrong that syntax was completely separate from semantics (which I think he believed when he wrote that example).
BruceS,
It may well be valid in predicate logic. It is not a valid argument form in propositional logic, because you need to understand the quantifier “anything” to show that the conclusion could not be false if the premises are true. Propositional logic doesn’t require understanding the premises–you just assign truth values to the propositions. And you have three different propositions there, so you can’t get a valid form of argument. Once you start mucking around inside the premises you’re not doing propositional logic anymore.
And, to repeat for the 20th time, affirming the consequent is a fallacy of propositional logic.
That rang a bell.
I took a Coursera course on logic at one point and it claimed that any argument from premises A1, …, An to conclusion B was valid iff (A1 &….& An) => B is a tautology (where => means implies). . So chalk up another one for the inventor of truth tables.
According to the text, that result is a consequence of the Deduction Theorem which I don’t think Witt proved. Not that I am saying he made a lucky guess, of course.
ETA: After Walt pointed out my confusion about predicate versus propositional logic, I did recheck the textbook to confirm that the result was in the chapter on propositional logic (and it was).
OK, got it. ETA: I had missed the import of the propositional logic bit.
I’m no expert either. Fortunately what i’ve put on this thread is very basic stuff. I’ve taught introductory logic a couple times and phoodoo and nonlin are like the kids in the class who won’t do the readings or any of the hopmework because they’re sure they know it all already. Then, when they fail the final and only manage to get a D in the class, they complain about their grades and tell all their friends that logic is not only stupid, but wrong.
KN: logic is not my area
walto: I’m no expert either.
Me, just now: the whole of philosophy is bit of a blink-fest to be honest.
Creationists: WE WIN!!!!!!
The whole thing is arse-about-face. Evolutionary thinking did not pop up out of nowhere, followed by logic games to justify it. There were a bunch of facts requiring explanation – the nested hierarchy captured by Linnaean taxonomy, the resemblance of organisms to the fossils just under their feet but increasingly less with increasing depth, vestigial organs, adaptation … the existing paradigm didn’t cut it. It didn’t explain enough.
I’ve mentioned this before, but my own Damascene moment came aged 11; with the first issue of Animal Life, a partwork building into a full encyclopedia. I still have it. A pullout wallchart showed the basic evolutionary relationships. Of course! was my reaction. I was already familiar with the hierarchic Linnaean taxonomy, without giving it massive thought. Framing it in terms of a branching pattern of common descent made (and continues to make) perfect sense.
Here’s how nonlin might frame this: “If ‘evolution’ is true, one might expect a hierarchy of relationships. There is a hierarchy of relationships, therefore ‘evolution’ is true”. That’s not right. First, one observes a hierarchy of relationships. One wonders what could account for such a pattern. Common Descent is (IMO) the front runner from the off. But you can do more. If Common Descent is the reason, you’d expect all – at least, most – character states to follow that pattern. Once you have access to DNA sequences, you can track even the most trivial of substitutions or indels. Do they follow the pattern? Pretty much. Therefore evolution is true? No. Therefore it explains the data much better than any rival explanation.
Exactly right This was pointed out by both KN and I on the first freaking page of this bloviation festival. Deductive arguments for factual states or physical laws have disappeared since the 17th Century (unless you include Hegelian arguments for numbers of planets or other like speculations). Rationalism has gone out of fashion everywhere except in theistic circles. (E.g., Plantinga is fond of those types of arguments, as is our old buddy FMM.)
What does it mean to say one CAN assign truth values to something?
As I have said all along, propositions must have some rationality to them. At times you and Jock have said they don’t have to make sense, other times you say they do (you can’t keep your stories straight and that is why I have punched holes in them) …so now we are left with this vague statement that you “can assign truth” to something.
You have tried to blame Nonlin for not understanding your manipulations of arguments, but you all have not settled on what you mean yourselves.
“Might”, becomes “definitely won’t”, but “definitely will” doesn’t become “might not. ” That’s my favorite obfuscation in all of this.
…asks phoodoo, a couple of weeks too late.
He and Nonlin will never catch up to the rest of the class.
More than five years ago, in a much different TSZ, there is a lengthy discussion of the CR based on a post you did on intentionality. I wonder how the work in your latest paper would affect the thinking in your posts there.
That’s just a rhetorical question; I don’t think an OP in the current TSZ would be generate much interesting discussion.
Unless, maybe, there is some kind of quantum angle (phase?) I am missing.
That’s Inference to the Best Expalnation, of course, and philsophers have written books about it:
They even have the temerity to use IBE in philosophy, eg the IBE in the no miracles argument for scientific realism
https://en.wikipedia.org/wiki/Scientific_realism#No_miracles_argument
Now if you are saying that scientists can make observations without a background theory, then you will get some philosophical push back (eg what counts as a relation?). Of course, the background theory need not be (and probably should not be) related to the result of the IBE that uses the observations.
After you finish your book, if you are looking for a research topic for a new paper, you could combine your academic background with your experiences at TSZ to to produce a paper on “The Spinozan Roots of Intelligent Design Theory”.
Speaking of Spinoza, I just saw this on twitter today:
That’s interesting. Could be!
The relationships are those Linnaeus used to categorise. He was not proposing a genetic relationship, but a genetic relationship would give rise to that pattern. The clincher comes when we look at other character states – the ones Linnaeus did not use, not least because they were inaccessible. If otherwise independent, previously unexamined character states converge on the same pattern, that is powerful corroboration of the actuality of a genetic relationship.
Exactly. We can start with some background theory, and use it to make observations, possibly combine them with other observations based in other background theories (eg genetics), and then generate a new theory (or confirm an existing theory) by IBE.
I’m agreeing with you; just applying a bit of philosophical cake icing and/or humor to go with the quantum puns in other posts.
Need I add that It’s humor according to my background theory of humor?
Pithy.
Have you seen this Stone variation on the democracy-does-not-work-for- humans theme?
Democracy Is for the Gods
I hadn’t seen that, thanks. You’re a great resource.
(Although there was also a bad thing about seeing it: I was unfamiliar with the 2006 Woodruff book mentioned in it, and I probably should have at least heard of it. So, I mean, uh, Thanks a lot!!!)
Spinozism is incompatible with intelligent design, because Spinoza’s God is not a Mind that is ontologically distinct from the things it creates, nor does Spinoza’s God make any choices about what to create or not.
Spinoza’s “pantheism” really amounts to the following: (1) the infinite power that traditional theism ascribes to God actually belongs to the Universe (“Deus sive Natura”); (2) the fullest development of human virtue includes an experience a reverence and awe for the Universe that traditional theism reserves for God (“amor dei intellectualis”; (3) a theoretical understanding of the Universe is the only part of the human mind that survives the death of the body and is therefore truly immortal.
I wonder if the author would have reached a different conclusion if he had taken into account non-Western experiments with democracy and collective decision-making in hunter-gatherers.
Hey, I said it was a research project. I did not say it was an easy research project.
I think Walt is spot on using rationalism to describe a worldview commitment of ID theorists and their TSZ acolytes.
No doubt it would be easier to work with a Christian rationalist when giving an intellectual history of ID philosophy, but I thought Spinoza would be better for Walt because (1) IIRC he did his PhD work on Spinoza and (2) Walt clearly loves a challenge (viz his posts in this thread, as just one example among many here at TSZ).
IDers are adamant that they assume nothing about the
Ddesigner. So perhaps one can argue for a pantheistic (pancomputational?) designer. Spinoza’s single substance for the universe is nothing other than Information and its conservation in evolution is part of the expression of its varying modes.But ’nuff said by me. I would not want to do Walt’s work for him.
I do think that he has an opportunity here for Templeton funding.
Moving from Spinoza back to democracy (but remaining far from “Affirming the Consequent” since trying to explain what that is hasn’t really gotten anywhere), I’m very unhappy to report that after reading “Rucho v. Common Cause” that I think Roberts did a better job than Kagan did. It’s quite hard to make a case for anything resembling a decent democracy using only the U.S. Constitution, holy mess that it is.
In 1901, Congress passed a reapportionment act that contained this:
But, alas, it didn’t stick.
ETA: I mean the compactness requirement (which might have helped here) didn’t stick. The unfortunate requirement for single member districts is, of course, still with us.
So little democracy in this country……
In a rational world, that would be the end of the thread.
So what? You’re not disputing anything in this OP and are not contributing anything by noticing the trivial: “replacing A with B we get B”.
You’re in the wrong thread.
Seriously? Never funny on purpose. Always funny involuntarily.
WTF are you talking about?!? You agreed with everything here and now you’re backtracking? WHT is wrong with you?
DNA_Jock seems dishonest at this point. Very disappointing.
Let’s not use their wooden tongue: “evolution” has nothing to do with science.
Then count Coyne as a nobody with his “why evolution is true”. And everyone else too as all (100%) arguments for “evolution” are of this type. But to prove me wrong, you need to find just one (1) that doesn’t follow this format. Can you do this SIMPLE TASK? This is a repeat ask. First time you returned nothing and that’s exactly what you will return this time.
If true, this fully explains the sorry state of the education system.
It popped out of atheism. Atheistic religion first, “proof of evolution” fallacy after.