Is fallacious logic really bad...or even wrong?

"fallacious logic" is not logic at all to me.

However, one has to keep the Fallacy Fallacy in mind: Just because Bob's demonstration of X is fallacious, isn't enough to move X from "unproven" to "false".

Fallacies point when something is failing logically, not when something is untrue.

For example I can say "All <insert nationality here> are subhumans. He's not subhuman, therefore he is not <nationality>". The logic of that is correct, despite being obviously untrue. The opposite also happens, you can have a fallacious argument with the core of the argument being true, the structure is the part of the argument that is flawed.

edited 13th May '12 1:06:25 PM by Anfauglith

Wha, it's confusing because we're talking about multiple kinds of fallacious logic.

I guess my point is that calling it a fallacy is situational. It's fine to use a reasoning that relies on some rather obvious assumptions, so long as the audience is in the same picture as you are. If the audience is not convinced in that assumption and you insist on pushing it, then it becomes a fallacy.

There is another thought.

There's the Slippery Slope fallacy, which almost everyone is familiar with (don't take marijuana, you'll end up a crack-whore sort of thing). But what not everyone is familiar with is Reductio Ad Absurdum, which is taking an argument to its logical extreme.

There's a fine line between one and the other, and crossing it is quite simple.

Fallacious logic is bad logic, but bad logic isn't inherently wrong (answer). Being right is the destination, logic is just the set of directions to get there. So bad logic is the equivalent of turning left instead of right. You might still end up where you wanted to go, but you didn't use a good set of directions so you can't really treat it as reliable. Axioms would be the starting point and evidence would be the road signs, yay for extended metaphors!

This is a really important point to make here, because it's a goof that people on this subforum make very, very regularly. Slippery slopes happen all the time; the fallacy is in assuming Bad Conclusion X is the only possible result, but being wary of it happening and guarding against it isn't remotely fallacious.

And as for what's bad, there are several instances in game theory where everyone acting logically will result in a universally sub-optimal outcome for all players, so not even correct logic is always "good".

Yeah, I know I've seen several times where someone has made the statement "I disagree with blah, because according to precedent, there's a good chance of blahblah happening." and it got called a slippery slope argument.

There's also an irritating trend of people calling genuine misunderstanding or disagreement a fallacy of some sort, or people ducking an argument entirely by calling it a fallacy.

False data isn't a fallacy, unless you consider perfect information a given. Disagreement also is not a fallacy provided it's either axiom or information related (ie: whether or not you consider something Worth It). The last actually is something of a problem. When an argument is a fallacy, it's simply a mooted argument, not a counter argument.

The slippery slope fallacy is only a fallacy when there's nothing to suggest that the next step would inevitably follow from using the same logic.

Fallacious slippery slope: allowing gay marriage will result in allowing people to marry children or animals. (Gay people are, unlike children or animals, consenting adults. The logic is "we should allow all consenting adults to marry", so the slippery slope argument is bad.)

Not-fallacious slippery slope: if we support free speech for mainstream political stances, then we'll inevitably end up supporting free speech for fringe politics like Communists and Nazis. (The logic is "if you support political free speech, then you have to support it for everyone, no matter how repugnant you find their beliefs". This is true.)