Logical fallacies are errors in reasoning, i.e.: arguments that violate the rules of logic.
They often arise spontaneously for a lack of attention in reasoning, or a flawed comprehension of logic, but in many cases they are intentionally used for the purpose of deceiving the other party, or dishonestly winning an argument.
Treating two unrelated statements as if one of them was a consequence of the other one.
Ex.:
"I just finished eating an apple, therefore it's going to rain."
Using the same word with 2 or more different meanings in the same context.
Treating 2 or more different concepts as if they were the same on the basis of them being identified by the same word.
Ex.:
"Feathers are light, so they're useful against the darkness."
Attempting to prove a thesis by using an argument that inherently assumes the thesis to be already true.
Ex.:
"God exists because that's what the Bible says, and the Bible is infallible since it's the word of God."
Inverting hypothesis and thesis.
Attempting to prove an hypothesis by assuming the thesis that derives from them to be inherently true.
Ex.:
"I am a good person; therefore, whatever I do is good."
(P implies Q), Q => P
Mistaking a necessary condition for a sufficient one.
Assuming that something is true because one of its implications is true.
A faulty version of the "Modus ponens" law of inference.
Ex.:
"When it snows it's cold outside. Now it's cold outside, therefore it's snowing."
(P implies Q), not P => not Q
Mistaking a the denial of a sufficient condition for the denial of a necessary one.
Assuming that something is false because it's the implication of something false.
A faulty version of the "Modus tollens" law of inference.
Ex.:
"When it snows it's cold outside. Now it's not snowing, therefore it's not cold outside."
Ax,P(x) => Ex,P(x)
Assuming the existence of something on the basis of the existence of a general rule about it.
Ex.:
"All dragons breathe fire, therefore dragons exist."
Ex,P(x) => Ax,P(x)
Using single examples as proofs of a general rule.
Ex.:
"This dragon breathes fire, therefore dragons breathe fire."
Treating a problem as if it had only 2 possible solutions.
Ex.:
"That guy hates the sea, so he must love the mountain."
Assuming that a halfway solution between 2 alternatives is necessarily the right one.
Ex.:
"A state of constant war is bad, but eternal peace is also bad: we should have wars, but only every once in a while."
Attributing to the whole the properties of its parts.
Ex.:
"This house is made of cubic bricks, therefore it must be cubic."
Attributing the properties of the whole to its parts.
Ex.:
"This house is cubic, therefore it must be made of cubic bricks."
Rejecting an argument by refuting a completely made up one and implicitly attributing it to the opponent.
Subtly changing the opponent's argument with a different (and more easily debunked) one and addressing that instead of the original one.
Ex.:
"Death penalty is not the right solution."
"If we never punish criminals, society is doomed to collapse."
Subtly changing the subject of the argument in order to avoid admitting being wrong.
Ex.:
"This proves it's not true that my team is losing."
"Your team's players take drugs in order to win."
Using a refutation of a particular proof for a thesis as a refutation of the thesis itself.
Ex.:
"The arguments in favor of your thesis have been debunked; therefore your thesis is false."
Accepting and/or rejecting an argument on the basis of its proponent moral and/or intellectual characteristics.
Ex.:
"The guy who said that is known for saying a lot of stupid things, so it's false"
Arguing that something is true just because a lot of people believe it.
Ex.:
"If everyone agrees that the Earth is flat, who are you to say otherwise?"
Arguing that something is true just because that's what the experts say.
Ex.:
"The experts agrees that the Earth is flat, who are you to say otherwise?"
Rejecting an argument just for having been used too many times.
Ex.:
"We already heard that argument over and over again, it's becoming tedious."
Rejecting an argument on the basis of its proponent having personal motives for supporting it.
Ex.:
"You only say I'm corrupt because you want to kick me off my position and take my place."
Treating a reaction to a false accusation as a proof of the accusation.
Ex.:
"Stop saying I raped you! It's not true!"
"The fact that you get so mad about it tells you're guilty."
Arguing that something is good just because it's new.
Ex.:
"Of course this car is better: it's the latest model."
Arguing that something is right or wrong based on whether it is natural or innatural.
Ex.:
"In nature there are no animals who wear hats; therefore, wearing hats is immoral."
Arguing that something is right or wrong based on whether it is natural or innatural.
Ex.:
"Since animals do not wear hats, not wearing hats it's like being an animal, therefore it's immoral."
(work in progress...)