Philosophy Logic question Only those who took logic please?

Question

What are logical constants and variables? Give examples.

One more please if you can.

Explain the differences between logically true, contingent, and logically false statements. Give examples of each. Remember: scientific statements or other universally true factual statements are not necessarily (or even usually) logically true statements

Thanks much!

Answer 1

Yagami:

This is a question I am afraid not many will know how to answer, I had to think and do some research to refresh my mind about your question, and i must admit that I had forgotten such an elemental part of logic that as a philosopher I should never neglect, thank you for the question. But here is your answer, limited as it may be, it is offered with esteem:

In symbolic logic, a logical constant is a semantic symbol that has the same value for all models, such as "true, false...not, and, or, if...then, equals, neccesary, possible, etc.

In symbolic logic, also variables are used to indicate an arbitrary element, basically variables are used to represent propositions that can be true or false.

"logically true" refers to a conclusion that follows from true premises. Such as: - All men are mortal, plato is a man, palto is mortal-. "Contingent" means that its validity is dependent upon something else, wether its a being or a statement, its vailidity or truth or its being is dependent on something else, such as if a, then b. b can not be unless a is first. l"ogically false" is a statement that is untrue, does not correspond to reality, but is not necessarily a lie, it could be that this conclusion is logically valid but the premises are not true, since the truth of a conclusion depends on the truth of the premises. Wether this stament is true or false it may or may not be intended to deceive, therefore not a lie or deceipt but simply ignorance, a typical example of this kind logically false statements is when we say: "I am a fool" and this comes from the following reasoning;

Fools make mystake, I always make mystakes, I am a fool. But one of the premises is wrong, because everybody makes mistakes by nature, if we follow this reasoning to reductio ad absurdum that would mean that we all are fools, which is not true. It is also not true that i always make mistakes, etc.

Hope I helped you some, or i maybe told you what you already know and I wasn't much help. but in any case I wish you the best.  

cheers.

Answer 2

Have you checked Wikipedia?  Many of their explanations and examples make lots more sense than what you'll find in your logic textbook.

There are also lots of excellent web sites dedicated to logic and critical thinking.  You might want to look them over and bookmark them for later in your class.  Here are a few that I use as a reference; a Google search will find many more.

A site about critical thinking and how to develop logical arguments:

http://www.hebrew4christians.com/Clear_T...

A thorough discussion of logical fallacies

http://www.nizkor.org/features/fallacies...

A site discussing the use of statistics as proof in logic, and a discussion of various types of fallacies:

http://www.numberwatch.co.uk/number%20wa...