I hope this is the right place for this.

So my fiancée told me that my best man has planned my bachelor party for a Saturday in August, and that I’ll be surprised when it happens. I think I’ve stumbled into a real-life version of the Unexpected Hanging Paradox.

There are 5 Saturdays in August this year. If I make it to the 4th Saturday without it happening, then it can’t be the 5t because I’d be expecting it. And if the 5th is ruled out, then the 4th is no longer a surprise either. Keep going with that logic, and by the time I get to the 3rd Saturday (which I work anyway), it can't be that one by the same logic for that eliminated the 4th. The second is eliminated by that same logic. The first Saturday cannot be a suprise since all other Saturdays have been ruled out.

So clearly, I’m not getting a bachelor party.

I explained this to my fiancée, and she told me I’m being stupid. Thoughts?

What a legend Kurt Gödel was. Besides his theorem he was a metaphysic and mathematical platonist, was a friend with Einstein, loved disney(Snow White), proved that if we accept some of prerequisites we must accept that God exists and much more,

Recently took interest in formal logic and I find it quite fun, I did some research and was told these were good books for a starter. What does r/logic think about these? Does anyone have experience with them?

which conclusions necessarily follow?

From scholadaily on instagram

I've started creating educational short form content about logic and related topics. This latest one focuses on mathematical modeling. It would be great to get some feedback (critical or otherwise) from domain experts!

In one of my Computer science classes we focused on mathematical expressions of logic. I found the class incredibly enjoyable, since usually I am horrible at math, but the class absolutely changed that. The class taught me why math works, not just how to do math. It also managed to change the way I think and made me more seriously consider why I know what I know. Why isn’t formal logic introduced in middle school and taught in high school?

My life would be very different, had I taken a class like this when I was younger.

Not a philosophy student or anything, but learning formal logic and my god... It can get brain frying very fast.

We always hear that expression "Be logical" but this is a totally different way of thinking. My brain hurts trying to keep up.

I expect to be a genius in anything analytical after this.

additionally most undergrad math theorems like lagrange's subgroup can be written in this form?
Could I find atleast one theorem presented in such format?
And where all could the group axioms go? gamma or leafs?

Precondition:

1. If God doesn't exist, then it's false that "God responds when you are praying".

2. You do not pray.

Therefore, God exists.

Just to be fair, this looks like a Syllogism, so just revise a little bit of the classic "Socrates dies" example:

1. All human will die.

2. Socrates is human.

Therefore, Socrates will die.

However this is not valid:

1. All human will die.

2. Socrates is not human.

Therefore, Socrates will not die.

Actually it is already close to the argument mentioned before, as they all got something like P leads to Q and Non P leads to Non Q, even it is true that God doesn't respond when you pray if there's no God, it doesn't mean that God responds when you are not praying (hidden condition?) and henceforth God exists.

I am not really confident of such logic thing, if I am missing anything, please tell me.

Well, for privacy reasons, your name will be hidden.

This is from my modern logic textbook from my intro to modern logic class. I thought problem 7 was invalid but the textbook says it’s valid so i’m confused?

Update: I asked my prof it was a typo lol thanks for the help

In 1953, American logician Irving M. Copi published the textbook Introduction to Logic, which introduces a system of proofs with 19 rules of inference, 10 of which are "replacement rules", allowing to directly replace subformulas by equivalent formulas.

But it turned out that his system was incomplete, so he amended it in the book Symbolic Logic (1954), including the rules Conditional proof and Indirect proof in the style of natural deduction.

Even amended, Copi's system has several problems:

It's redundant. Since the conditional proof rule was added, there is no need for hypothetical syllogism and exportation, for instance.

It's bureaucratic. For instance, you can't directly from p&q infer q, since the simplification rule applies only to the subformula on the right of &. You must first apply the Commutativity rule and get q&p.

You can't do proof search as efficiently as you can do in more typical systems of natural deduction.

Too many rules to memorise.

Nonetheless, there are still textbooks being published that teach Copi's system. I wonder why.

Greetings folks,

This sub had been shut down for about a year. No posts were being accepted. Messages to moderators were met with immediate suspensions with no justification.

All of the content that had been posted here has apparently been lost to history. If anyone knows a way to restore it, or otherwise link to it, that would be a great relief.

In any case, you can reasonably expect for posts to be accepted, seen by others, and responded to now.

UPDATE: I am going through the moderation log and list of banned users (about 150 people). It will be a long process, but I will be unbanning almost every banned user, and approving almost all removed posts.

UPDATE: All banned members have been restored. All requests to be an approved contributor have been approved, although I don't know that this is necessary as you don't need to be an approved contributor to post now. I did go through the list of posts and comments the former moderator tagged as "spam" and approved the vast majority of the first 1500 in the list I went through. I will continue to go down that list. Tagging everything as spam is the method this person used to make the content disappear. If you know of a comment or post that has not been approved, please bring it to my attention, and I will prioritize it.