## quick formal logic question

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macaulian

Posts: 85
Joined: Wed Jan 20, 2010 6:11 pm

### Re: quick formal logic question

SOCRATiC wrote:
macaulian wrote:
Ok, this is very wrong. First of all, this is predicate logic, not symbolic logic. Second, as someone who has taken logic, written papers on the subject, and taught a logic class, I can tell you that anyone who says "empty set" in reference to PL is BSing you. Once again, you cannot assume something exists in logic unless it is given. For example, here is modus ponens:

a->b
a
therefore, b

Without providing a, you cannot prove b. Never assume something not given. Most of the time something may or may not be true, and you are saying that is something may or may not be true, assume that it is true, that is absolutely wrong.

In Symbolic Logic, you have Propositional Calculus AND Predicate Logic. Predicate logic is a subdivision of Symbolic Logic, you dimwit. The demonstration of your ignorance of this fact completely undermines the credibility boost that you attempted to achieve by mentioning your credentials (taking a logic course, writing papers, and teaching the god damned subject).

What I meant to say is that it is not simple symbolic logic, it is more advanced predicate logic. Would you agree with this? I will edit the post. I want people to understand the difference between the basic rules and what happens when you add for some, for all, and there exists.

SOCRATiC

Posts: 114
Joined: Sun Jan 24, 2010 4:22 am

### Re: quick formal logic question

NewtonLied

Posts: 77
Joined: Sat Feb 20, 2010 6:16 pm

### Re: quick formal logic question

Here's one for you:

Arrogant people will refuse to admit they are wrong
Arrogant people will occasionally be wrong

For the purposes of this question, you can assume this thread as proof that the antecedent exists. I'm going to watch TV. Good luck, OP.

CMDantes

Posts: 420
Joined: Thu Feb 04, 2010 2:37 pm

### Re: quick formal logic question

NewtonLied wrote:Here's one for you:

Arrogant people will refuse to admit they are wrong
Arrogant people will occasionally be wrong

For the purposes of this question, you can assume this thread as proof that the antecedent exists. I'm going to watch TV. Good luck, OP.

I approve of this.

SOCRATiC

Posts: 114
Joined: Sun Jan 24, 2010 4:22 am

### Re: quick formal logic question

NewtonLied wrote:Here's one for you:

Arrogant people will refuse to admit they are wrong
Arrogant people will occasionally be wrong

For the purposes of this question, you can assume this thread as proof that the antecedent exists. I'm going to watch TV. Good luck, OP.

+1, and: macaulian -

There is no need to bring in topics about existence in his situation. We assume that it exists, since we're not trying to solve a formal PL equation.

Go visit your local logic professor, and show him this:

SOCRATiC wrote:
All B are A
All B are D
Therefore some A are D
-----------

"All B are A" means that some A are B. If some A are B, and if all B are D, then it must be true that some A are in fact D.

He will say that I am correct. You can claim that you've done it in order to obtain the boost in ego and self-esteem that you've pathetically attempted to gt from this post.

If you don't have time for this, go to your desk, take out a box of crayons, and draw up a couple of venn diagrams. You'll still see that I am correct.

EDIT:

OP - Trust my judgment.

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JJDancer

Posts: 1564
Joined: Sun Jul 26, 2009 7:41 pm

### Re: quick formal logic question

NewtonLied wrote:Here's one for you:

Arrogant people will refuse to admit they are wrong
Arrogant people will occasionally be wrong

For the purposes of this question, you can assume this thread as proof that the antecedent exists. I'm going to watch TV. Good luck, OP.

lol +1

Thank you everyone I really did not mean for this to get so complicated. In the question I created I intended there to be Bs and As and Ds. (*gasp* they do exist!)
I do appreciate pointing some of you pointing out that that would need to be stated/ the aspect about combining rules like ray goes first etc etc.

Thanks all.