She

 

You mean modus ponens? Keeps popping up. Weird how that happens, isn't it?

 

I only wish I could take credit for it. Greek thinkers and they really were quite brilliant.

 

If you are not trolling(which seems pretty likely at this point) I would guess that you are failing to understand the need for substitution and more broadly the relationship between statements you were told are true and equalities.

 

Really what you chose to do with this information is up to you at this point.

Yet another "useful" answer...

Well, I guess this has been a completely waste of time. Thank you. It surprises me, you know what a basic Modus Ponens is! So 1 + 1 = 2 right? amazing.

I'm really starting to think, you really believe that you know what you are talking about. Self-delusion is called this.

That's it. I find that no one here knows about this, thank you very much for teaching me about nothing.

Reminder for all of you: if you don't know, you don't have to answer, it's ok to not know. What is shameful is to pretend you know about something of which you are clearly ignorant.

Regards.

!

Moderator Note

The people posting here quite obviously do know the answer

I wouldn't be so sure of that, ha, ha, ha.

Thank goodness! these people will be very grateful with you Mr. Moderator, you have save them of making themselves look like fools. Is it so difficult to say: I don't know? They were not obliged to answer, were they?

If P then Q. Best answer to a proof by inference I have ever heard. It is like saying that a math problem is solved given 1 + 1 = 2. Brilliant!

They were not even able of giving me a hint about how would be the premise number 4. Reminder for me: "no to be so rude with people trying to "help".". And reminder for them should be: Not to talk about what they don't know.

Have a good night.

 

If (Nobody knows the answer), then (No answer presented)

(No answer presented)

Therefore (Nobody knows the answer)

 

1. If P, then Q.
2. Q.
3. Therefore, P.

Which is a logical fallacy. If nobody knows the answer then you can logically prove there will be no answer presented.

 

1. If P, then Q.
2. P.
3. Therefore, Q.

 

But there not being an answer presented does not prove that nobody knows the answer.

 

It benefits you to learn the process of thinking logically in a formal fashion via help, not through receiving an outright answer.

You've been given the rule for the next step multiple times. If you can't see it from that, you need to go back and review your rules as the last two are two of the most commonly used rules.

Just say you don't know. Be honest.

Good bye.

Ok, I think no one knows. You don't have to "answer", or at least be honest and say you don't know. You are making others waste their time.

Thank you all for your "help".

!

Moderator Note

The replies are attempting to "Help". We don't have a "Homework Answers" section.

 

Sorry.

Where am I saying it is homework? it is Not. I'm just asking if someone who really knows about this could help me. Until now, no such person has answered. Thank you for your "help".

Yes, must prove S. What do you know about E? What can you say about (FvE), or D, etc?

 

 

Since this is "homework help" I don't think I can just give a solution, but try this simpler example.

 

1. P -> Q

2. P :. Q

 

What are we proving? Given premises P -> Q, P, prove the conclusion Q.

How, informally? We're given that P is true. Since P implies Q, Q is also true.

How, formally? Modus ponens is the rule to use. Do you know what the proof should look like?

There are 3 premises:

1. (F∨E)→~D

2. S∨D

3. E

And a conclusion:

S

I know what a premise is, and what a conclusion is. Don't beat around the bush and help me solve it if you do know how to.

Thank You.

I think you don't even know what you are talking about, "if P then q" is just one conditional. Solve the problem if you know how to. Thank you.

@md65536

The same here, solve the problem if you know how to, and check it. Do you know what should be proved? The conclusion is S, do you know how to reach it?

Good night, I´m trying t o learn by myself a little about formal logic, but it has been difficult. I understand what are the logic rules involved but I don´t know how to solve problems.

For example, I don't know how to solve this:



1. (F∨E)→~D
2. S∨D
3. E ∴ S

It seems easy, but I don't even know where to start. If someone could help me, I would be very grateful.

Thanks.

PS: If you could validate it with this checker, better yet it's proof #3: http://www.poweroflogic.com/cgi/Proof/checkprf.cgi?exercise=8.1C