I daresay actual Philosophers have a name for what I'm about to say in this blogpost, but I can't seem to find it on Wikipedia. I should probably stop relying on Wikipedia for my philosophical education. Here, though, on formal fallacy:
As modus ponens, the following argument contains no formal fallacies.No it's not, though. Maybe the Council have erected a giant awning over the street. Maybe it was a localised shower, and the wind blew the rain out of the way. Maybe it rained an hour ago and the street has subsequently dried. You take my point.
1.If P then Q
A logical fallacy associated with this format of argument is referred to as affirming the consequent, which would look like this:
1.If P then Q
This is a fallacy because it does not take into account other possibilities. To illustrate this more clearly, substitute the letters with premises.
1.If it rains, the street will be wet
2.The street is wet.
3.Therefore it rained.
Although it is possible that this conclusion is true, it does not necessarily mean it MUST be true. The street could be wet for a variety of other reasons that this argument does not take into account. However, if we look at the valid form of the argument, we can see that the conclusion must be true.
1.If it rains, the street will be wet.
3.Therefore, the streets are wet.
This statement is both valid and sound.
Do you, though? It is more than just to nitpick with that particular example. It is to say: there is no situation in the world which cannot be so nitcked. Thuswise nitpicken. 'Therefore it rained' does not follow in the third example, above, because, you know: maybe the streets are wet because a fire hydrant burst. But the same thing applies the other way around. Or more specifically, the attempt to rephrase the final example to exclude all the things that might falsify it -- as it might be, '(Assuming the council haven't erected a giant awning over the street, or that it was a localised shower, and the wind blew the rain out of the way, or that it rained so long ago that the street has subsequently dried etc ...) If it rains, the street will be wet' -- includes within it an 'etc' that potentially goes on forever. To quote the wiki again: 'This is a fallacy because it does not take into account other possibilities.' Ah, but there are always and inevitably other possibilities, no matter which way round you frame your argument.