Affirming the Consequent: A Formal Fallacy

This is a sample video from a video tutorial course titled "Common Valid and Invalid Argument Forms", which you can preview at the link above.

List of Tutorials in the Course

Part 1: Argument Forms Using Disjunctions (A or B)
1.1 Valid forms using "OR"
1.2 Invalid forms using "OR"

Part 2: Argument Forms Using Conditionals (If A then B)
2.1 Modus ponens
2.2 Modus tollens
2.3 Hypothetical syllogism
2.4 Affirming the consequent
2.5 Denying the antecedent

Part 3: Argument Forms Using Generalizations
3.1 Valid and invalid forms using "All"
3.2 Valid and invalid forms using "Some"

[marleeashton]

Thank you so much for making these videos!!! I have a midterm tomorrow and you're saving my ass, these examples are awesome.

[bjjace]

I have a question. I'm a 24 year old Grad Student working towards my MSW. To be clear I'm in an internship at a Drug Rehab. I must complete this internship to be a future social worker.
We drug test and BAC the patients randomly. We have a strict policy that states :
"if a patient tests positive on the BAC machine which tests for alcohol. We are not allowed to administer a retest.
When asked why we can not perform a retest.
The "higher ups" claim " retests mean we don't trust our equipment".

To me this not logical, because many things can cause a positive BAC especially in the time of Covid-19. People using hand sanitizer and wipes.
I don't want to get in to a conversation about drugs or false positives. I'm requesting your opinion regarding this policy. Is it logically sound?
Is this policy guilty of affirming the consequent?
Any help would be greatly appreciated..

[kierand]

1. If I read the pages of a book then I finished the book
2. I finished the book
3. Therefore I read the pages of the book.

[RefutingSkellyism]

Thank you very much for these videos. It seems that defining and labeling the many types of fallacious arguments really helps clears the mind and stay focused on the most important aspects of an argument, and in consequence the weakest links your opponent is relying upon.
What else is interesting, is that rightly discerning these logical fallacies, really shows that all Hegellian dialectical forms of argumentation, are based upon 'Affirming the Consequent' or a corruption of Modus Tollens. NO?

[عبداللهرويشد-كو]

I think the fallacy can be broken by inserting the word: probably. Although, this word means what it means.

[PhilosophyFreak]

@RefutingSkellyism Ah, I see. It's either A or B, it's not A, therefore it must be B. The problem with this kind of black-or-white thinking ("false dichotomy" is another term for it) isn't with the logic, though, it's with the truth of the main premise. If you grant the main premise (that A or B must be true) the logic works fine. You challenge these kinds of arguments by noting that the main premise is dubious because it doesn't exhaust all the possible alternatives, just like in your example.

[robokill]

no, because it is not necessarily true that the conclusion is probable. it could be improbable. if you said "possibly", that would work, but then you aren't making the conclusion, which means that the fallacy doesn't apply anymore anyway.

[PhilosophyFreak]

@RefutingSkellyism Hi, and thanks for the nice comments on my channel profile. I'm not sure exactly what you're getting at with the hegelian reference. Can you give me an example of what you have in mind?

[Syllogist]

Why on earth did you declare the construction (0:14):

1. If A then B
2. B
- - - Therefore - - -
3. A
Is as invalid? Did you write the answer yourself and declared it wrong yourself?
:-)))

We carry out an elementary algebraic calculation (where B is the middle term):

1. If A then B (A->B)
2. B(B)
- - Calculation: ((A->B)*B)/B = ((AB+A'B+A'B’)*B)/B = (AB+A'B)/B= A+A - - -
3. A’+A
That is, the correct answer is: As it may be, so it may not be.

What kind of wrongness can we talk about here? Maybe just about yours?

[Cholo]

What kind of a person would use this type of so-called "reasoning"? (This is not a "rhetorical question.")

[RefutingSkellyism]

@PhilosophyFreak My reference of 'Hegelian', was hinged upon the Bi-polar dialectic, that estimates the values of 'significance', or, 'morality', upon linear thought: i.e.;Cold or Hot, Fat or Thin, White or Black, Right or Left, Right or Wrong, "It was Bush's fault, he was a 'republican', therefore vote 'democrat'". All the while, in three dimentional space (reality), Bush & Obama, are both bought, owned, & told what to do by the international owners of all the central banks. No argument there.

[infinitesimotel]

Good obs, yea the hegelian dialectic is based on perception manipulation. As long as they think it was their choice they will go for it. If you own all the factors then you can use whatever logic you like, because a situation is necessary to traumatize people into irrationality and lower modes of consciousness where they will simply make a choice out of self preservation. To swallow the bait hook n line. But yes, goes to show what sort of crap can be pulled.

[luanrachel]

the call example may be false simply because the person who calls lies.

[Rayvvvone]

I think this argument fails due to affirming the consequent. What am I getting rong?

1.If nor P, then not Q
2. Q
therefore, P

People tell this is valid, and I don't understand. Help ?

[cristop]

If there is racism there will be disparities disadvantaging minorities.
There are disparities to the disadvantageous to minorities, therefore there must be racism.
Apologies to all critical race theorists.