- 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
Since when are similarities enough evidence for common descent?!?
Does this remind you of anything:
“If common descent is true, then we should see similarities. We see similarities in biology. Therefore common descent is true.”
Hint: this OP. Of course, if you could PROVE the “if and only if” clause, then sure. Now, can you?!?
If regular cats have four legs just like regular chairs then both descend from a common ancestor?!?
You can see for yourself. Yes at Biologos, temporarily at PS, but censored too many times so the outcome is inevitable. Somehow, I am not a fan of totalitarian practices. Are you?
Nonlin.org,
Also on this thread.
🙂
There can only be ONE ultimate source of everything – it’s elementary. Hence monotheism. Don’t be confused by SUPERFICIAL differences between Judaism. Christianity, Islam, etc.
Probably beyond human capabilities to understand that. Can a cat understand biology? Can a dog understand physics?
Of course design is scientifically detectable. This has been discussed here: http://theskepticalzone.com/wp/intelligent-design-detection/ . As far as criteria and mechanisms, see above cats and dogs.
As shown, Behe’s EF is weak, hence this new Intelligent Design Detection procedure: http://nonlin.org/intelligent-design/ . Feel free to shoot it down if you can.
Would you rather read something bullet-proof or some weak nonsense like “the origin of species” just because it matches your prejudice? There’s no rush – it takes time to build something bullet-proof.
Obviously, the religion (atheism) came first and then the nonsensical “explanation”. Read about the pre-Darwin history of “evolution” and it will be very clear to you that Darwin is just the most persuasive of the false prophets of atheism.
Seriously? The Greeks has Cassandra while millions of gullible guys like you believed in Stalin, Hitler, Marx, Mao, Fraud, Darwin, etc. etc. You obviously still believe Banana was a great president – for some reason that goes together with Darwin. Low critical thinking capability most likely.
Well, they would consider themselves ‘benevolent dictators’ if it came to that conversation with them, though I doubt they’d have it. Joshua surely demonstrated what could be accurately called ‘totalitarian practices’, at least in making a kind of penalty box, demanding claims & statements by me, etc.
I don’t think he recognizes any imperfections in his scientistic Adam (with afterthought Eve) approach to this topic, which strikes at issues much bigger & deeper than his comp. biologist ‘fifth voice’ pretends to be able to address.
Do say more about what people shouldn’t be confused about re: superficial differences. Does it suggest you might be a Baha’i with anger primarily for atheism & skeptical godlessness?
I glanced at the linked page & see some adjustments from what is still a term largely, almost completely, controlled by the DI. Denis Lamoureux might be the loudest monotheistic alternative, with Adrian Bejan on the opposite, anti-religious atheist side.
You use capitalized ‘Intelligent Design’ & sometimes capitalize the single ‘Design’ in the presentation. Your “One Designer” hypothesis differs from the DI & is at least more honest about its ‘not strictly scientific’ basis for acceptance.
I don’t support common descent Behe and ID seem to …unless one we are talking about a common descent, such such as dogs from wolves…or variations within kinds…
OK. Submitted for review.
Is this a TRUE statement:
“If “evolution” is not true, organisms would not show consilient patterns of similarities and differences.”?!?
Are you claiming this?!?
Rest assured, sophistry will get you nowhere.
Not Baha’i 🙂
Read these:
http://nonlin.org/philosophy-religion-and-science/
And no anger. Don’t know where you live, but I like freedom in general and freedom of religion in particular as per the US constitution. Defending one’s freedoms is not necessarily ‘anger’.
Oh. So you don’t identify with any one of the Abrahamic monotheistic world religions, regularly attend a house of worship, focus on one sacred text and tradition above others? Is yours a mix & match syncretistic religious strategy?
The Pro-Con Notes are a nice touch, though the debate motion is not always specified, which confuses the target. Have you ever debated in public with someone on this topic? Or is this just armchair, amateur interest without training or familiarity with the relevant fields, figures & texts involved?
What’s the opposite of anger, the way you call it? I don’t see why you wouldn’t be angry at, for example, scientific fraud or forgery that deceived a generation of graduate students. Or when ideology swallows a movement of wannabe ‘revolutionaries’ chanting ‘strictly scientific’ to what actually turns out is an elaborate PR propaganda campaign?
What’s the run away from ‘appearing angry’ when indeed, it just looks like you’ve chosen unconventional & awkwardly worded terminology, in the same boat as the DI (even if, like PS & BioLogos, they don’t want you either). Your definitions of ‘design’ seem to me marginal at best & I either 1) disagree with them, or 2) mean something rather different when I use the term ‘design.’ I can see why people wouldn’t want to debate you in case they often don’t agree from the start with your definition of terms & if you cannot find common ground with them.
Baby steps, nonlin, baby steps. First, we need to tidy up the mess you made over “fallacies”:
Do you accept that the argument:
1) If “evolution” is not true, organisms would not show consilient patterns of similarities and differences
2) We observe consilient patterns of similarities and differences
3) Therefore evolution is true
is a logically valid argument? It cannot be a fallacious argument, contrary to what you appeared to claim when this argument was first put forward on this thread.
With that basic critical thinking homework out of the way, we can discuss the truth values of the premises.
That’s my hope.
DNA_Jock,
What do you call an argument, where the first premise is incoherent? Is it a valid argument?
For instance,
1. If DNA Jock is a baby killer, TSZ would be part of the global conspiracy of guerrilla online skepticism attempting to alter the realities of science in the public minds.
2. If number 1 is true, number 2 is true.
All this shows is that you can’t even tell the difference between premise and argument.
Thank you, phoodoo, for such an excellent example. Although I suspect you may be upset as to where it leads us…
Your first premise strikes me as coherent, if rather unlikely. Let’s use it to re-create the same argument that I have been putting to nonlin.
1. If DNA Jock is a baby killer, TSZ would be part of the global conspiracy of guerrilla online skepticism attempting to alter the realities of science in the public minds.
2. TSZ is NOT part of a global conspiracy of guerrilla online skepticism attempting to alter the realities of science in the public minds.
3. Therefore DNA Jock is not a baby killer.
Now, phoodoo, I am fairly confident that you will be unable to understand this at all, and will be reduced to random bluster and insult, but the argument presented in 1, 2, & 3 is a valid argument. It is not in any way a fallacy. Simply put, if 1 and 2 are true, then 3 is also true.
I am curious to see if nonlin will be willing to admit this.
If not A, then not B.
B
Therefore A
Or equivalently (Set X = not A and Y = not B)
If X, then Y
Not Y
Therefore not X
It is rather basic logic.
DNA_Jock,
I think you won’t be able to understand this, being a mathematician and all, but here goes.
Number one is not coherent, because we have no basis for making any such claims. It may be true, or may be untrue and it maybe have no correlation whatsoever.
Thus we can’t really just make any claim, say if it is true something else is also true and then claim that is logical. It’s on more coherent than saying ‘if blue is good ‘ five no longer equals nine. ‘
You can’t then say, oh well blue is not good , so five does equal nine ‘ .
It’s the problem with calling something logical, and being a mathematician.
phoodoo,
See Validity and Soundness.
If Jack is not wearing a red tie, he is not a Communist.
Jack is not a Communist.
Therefore, jack is not wearing a red tie.
Or
If Jack is not wearing a red tie, he is not a Communist.
Jack is a Communist.
Therefore, jack is wearing a red tie.
Perhaps this is why double negatives are considered bad style. They are hard to unwrap.
Even more confusing if the premises are questioned.
The more familiar example is:
If Jack is wearing a red tie, he is a Communist.
Jack is a Communist.
Therefore, jack is wearing a red tie.
Easier to see what is going on.
Nonlin could title it and do an OP!
More fun examples!
petrushka offered up three distinct arguments regarding Jack’s politics and ties.
Only one of them is NOT A FALLACY.
I’m betting that nonlin will be unwilling, and phoodoo unable, to tell us which one that might be…
Any takers?
All three are false, no?
The first one makes my brain hurt, but it looks like a fallacy to me.
It looks like the others to me.
If A then B
B
Therefore A
If Jack is (not wearing a red tie), he is (not a Communist).
Jack is (not a Communist).
Therefore, jack is (not wearing a red tie).
If (not A) then (not B)
(not B)
Therefore (not A)
Correction, this one is valid.
Modus Tollens
This is why I always had to debug my programs.
Guys,
I was hoping that phoodoo would be the one to set us all straight. Now we’ll never know.
The second bet — will nonlin acknowledge the validity of modus tollens or not — is still open. Any takers?
There’s an endless supply of human stupidity. Why would you want to punish yourself for it?
it”s a [somewhat] free country. Knock yourself out. And when you’re ready, we can discuss specifics.
Demonstrate this if you want to move on.
Let’s look at YOUR example in a neutral light:
1) If it doesn’t rain, the streets are not wet
2) The streets are wet
3) Therefore it does rain
Does this make any sense to you?
DNA_Jock,
I’m guessing he would. It’d be pretty embarrassing not to.
Nonlin.org,
I’m really hoping you get that that’s a valid form of argument.
Is the point of these useless exercises to demonstrate the OP examples do not apply to “evolution”? If so, say so and PROVE it.
I see no reason to follow you guys into sophistry.
“mo·dus tol·lens
[ˌmōdəs ˈtälenz]
NOUN
the rule of logic stating that if a conditional statement (“if p then q”) is accepted, and the consequent does not hold (not-q), then the negation of the antecedent (not-p) can be inferred.”
Now, is your conditional statement accepted?
“If “evolution” is not true, organisms would not show consilient patterns of similarities and differences.”?!?
“If it doesn’t rain, the streets are not wet”?!?
“If Jack is (not) wearing a red tie, he is (not) a Communist”?!?
“If DNA Jock is a baby killer, TSZ would be part of the global conspiracy of guerrilla online skepticism attempting to alter the realities of science in the public minds”?!?
If you think any of these is “accepted”, PROVE it. Else, end the nonsense.
You were right, Jock. 🙁
Like I said before.
Oh dear.
Err, yes.
My, are we being a bit forgetful?
You said that this OP was dealing with the logic fallacy, not with the truth of the premises. Have you changed your mind?
There’s an endless supply of stupidity and Nonlin is hoarding it all
Corneel,
Well, I think it is a logical fallacy to include in an argument a premise that we have no way to know, or ever know if that premise is correct. That is what makes it invalid.
You can’t follow with a second premise, when the first premise is nonsense.
1. If birds can fly, my aunt was a soldier.
2. Two is irrelevant. Because one is nonsense.
That would make all of mathematics invalid.
ROFL.
Nonlin, CrEaTiOnIsT gEnIoUs!
The easiest way to understand modus tollens is to see that it is extensionally equivalent to modus ponens: both inference rules tell us that the conjunction of p –> q, p and ~q is inconsistent. If p is the case, then q must be the case; if q is not the case, then p can’t be, since if p were the case then q would have to be.
They differ only in which of the premises ought to be rejected: modus ponens rejects ~q and modus tollens rejects p. (However, in actual reasoning, one might have better reasons for accepting both p and ~q — in which case one has reasons for rejecting the conditional!)
This is why I was fairly confident that petrushka’s triptych would make phodoo’s head explode:
Three distinct arguments, three conclusions:
Conclusion 1 : Therefore, jack is not wearing a red tie.
Conclusion 2 : Therefore, jack is wearing a red tie.
Conclusion 3 : Therefore, jack is wearing a red tie.
Arguments 1 and 3 are fallacious, number 2 is not.
Since phoodoo appears incapable of conceptual thinking, I was comfortable betting on his refusing to distinguish between arguments 2 and 3, because they have the same conclusion.
From nonlin, I just expected off-topic huffing and puffing, à la cordova. I did NOT expect nonlin to crash so badly. That’s sobering, given the OP.
Me either.
I’m too charitable, obvi.
phoodoo,
I think the error is that the second statement does not follow from the first. Evolution has not been demonstrated to be the sole cause of similarities and differences. This is simply Darwins inference.
Observations like genes not following the tree pattern are contradictory evidence to Darwins inference.
That’s the easiest way? 😉
In the world I live in, we say:
If the driveway is not wet, it hasn’t rained.
The driveway is not wet
Therefore, it hasn’t rained.
Are there people who do not find this construction easier to understand?
Not the easiest way to learn what the rule is, but it’s a way of really understanding why the rules are as they are.
Again, I’m not sure I’m following all this logic. Let me try…
If it rained, the streets are wet.
The streets are wet.
Therefore it rained!
This strikes me as wrong. Sure rain will wet the streets, but other things can also wet the streets. And therefore, if the streets are wet, we can hypothesize that rain was the cause, but that hypothesis must be tested. It can’t be inferred.
I think of this as inference not being reversible. p->q does not imply q, therefore p. This was presented to me in grade school as:
All tables have four legs
A cat has four legs
Therefore, a cat is a table.
We can correct this error by changing the first premise to:
ONLY tables have four legs.
Now we CAN infer that a cat is a table. I sometimes see “corrections” in this form.
Flint,
We’re trying to get Nonlin (and phoodoo) to understand the difference between validity and soundness.
Your first example is both invalid and unsound. It’s invalid because it violates the rules of logic, and it’s unsound because it’s invalid. To be sound, it would need to be valid and its premises would also need to be true.
Your second example is also invalid and unsound.
The third example is valid but unsound. The logic is correct, but the first premise is untrue:
The false premise renders the argument unsound.