Recent content by drguildo

Even if the intended meanings are equivalent, then thanks in part to the ambiguity of natural language and differences in interpretation, the end results certainly aren't. I hate to break it to you but your command of English isn't that great and I found the explanation I pasted much easier to...

Hehehe, I figured you held this fundamentally incorrect view. I suppose it's what leads you to post comments (unless I misinterpreted you) such as #28. That is, if somebody does not understand one (or two, three etc.) explanation of something, then they cannot understand any explanation of it...

The explanation in your post was fine and answered my question, but only in the context of a proof of the principle of explosion which you said was contained in a previous post of yours, but which I couldn't (and still can't) "see". Once I read the proof I cited then it clicked. Not all...

Why? Is the explanation I pasted incorrect?

It seems to me you just restated proof by contradiction. I found this nice explanation on Everything2:

I sure would. From what I can gather, it was a restatement of previous posts, but yes. I have. Yes. What is the benefit of being able to conclude anything beyond the opposite of the proposition that led to the contradiction?

I don't have a problem understanding this. It makes sense at least in the context of the law of excluded middle. However the book I'm reading states more than this, as you can see in posts #7 and #12.

Okay, so why not say: if we assume ¬F, blah, blah, blah, we reach a contradiction, therefore we conclude F must be true; rather than concluding anything we want.

Yes, we've already been over that. What I want to know is what's the point.

Okay, but this raises the question what is the point in deducing something from a situation that is never going to be able to arise in order to lead to it? I also still don't understand how it can be used to justify or-elimination.

So we're not really inferring anything from Marilyn Monroe kiss scenario, it's just that we can state whatever we like because it's impossible (cf. contradiction)?

What I don't get is how it's used to validate certain inferences. My understanding is that any path of reasoning that leads to a contradiction is fallacious and should be abandoned with nothing inferred from it except the opposite case (at least in classical logic which has the law of excluded...

Indeed, if a square has to be one of X, Y or Z, and you know it isn't X or Z, then it must be Y (queue Sherlock Holmes quote). But I don't understand how this relates to the formal rule of negation elimination and it's relationship with contradiction which states that should you encounter a...

Thanks; that's a good intuitive example of how contradiction can be a useful tool in reasoning, but I think I'm being misunderstood when I say you can conclude "anything" from a contradiction. I literally mean anything. For example, the book I'm reading (Proof and Disproof in Formal Logic)...

I have played Sudoku, I don't see the relationship though. Especially not when it comes to being able to deduce anything from a contradiction.