It's been happening since whenever the first two simultaneous philosophers lived. — whollyrolling

What do you mean by that?

Sometimes even then they're still not aware it, or are in denial. — S

Same as above...

Sorry misread your comment. A fallacious argument is a contradiction. As mentioned above, contradictions allow you to deduce anything. — Devans99

OK, thanks!

Yes if a logical error is made in the derivation. There is a set of valid derivation rules called syllogisms. If you don't stick to these rules you get invalid conclusions. — Devans99

So, then you can have some unchecked logic going about that is faulty; but, never actually true because nobody wen't to the matter of assessing the truth or falsehood of it?

If an argument is derived from valid premises and the derivation is valid logic, then it is a valid argument. — Devans99

Yes; but, can it be the case that an argument that is fallacious can lead to other arguments that are fallacious?

Anything following on from it is also valid (provided the derivation is valid). — Devans99

Yes, though, in the case of fallacious arguments, then the same "logic" could apply but be mistaken and faulty, yes?