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.