Logic Fallacy =  Bad Argument.

If you have every argued with another human (and if you read this blog then I bet that you have) at some point you have certainly heard logic fallacies.


Recognizing and discrediting them is an easy way to win almost any debate. Even when you are in the wrong. But, like a timely joke, it’s so hard to remember them when you need them.


No longer! In this series we present the most common logic fallacies in their most basic forms


Here’s number four in our “Easy-Peasy guide to Winning Arguments and Losing Friends”. But don’t worry, most of your soon to be ex-friends are fallacious losers anyways.

Number 4

Affirming the Consequent

(frequency: scarce)
(aka: Converse Error)

Simply put: If A then B, B so A

This one is easy and only sounds hard when over explained. So I will just show you.



If you go swimming (A) you get wet (B). True

You are wet (B) so you went swimming (A). False


See how first part is true and the second part is fallacious. That’s because the conclusion does not follow the premise.


Defense: The best defense against Affirming the Consequent is just to recognize it when presented. Once you recognize it you can shoot it down quite easily by adding a second conclusion (C)



If you go swimming (A) you get wet (B).

You are wet (B) so you went swimming (A). Actually I just took a shower (C).


Once more, don’t overthink Affirming the Consequent, just recognize it.


More Examples:


If the Devil is real, then mankind will do wicked things.
Mankind does wicked things, so the Devil is real.


When I snort cocaine, I don’t sleep well.
Last night I didn’t sleep well, I must have snorted cocaine.


When you cheat on your spouse, you are often away from home.
Jane is often away from home, cheating bitch!




WARNING:  If the conditional is replaced by a bi-conditional (if and only if) then the Affirming the Consequent can be valid. This is because the consequent has been limited to one specific event.


You will usually often notice an “if only…”, “just when…” or some kind of modifier making it a bi-conditional statement.




If, and absolutely only if, I win the lottery I will buy a Lamborghini,
I did buy a Lamborghini, so I must have done the lottery.