Study Guide: Lesson 4
A Little Logic
Logic is the primary tool or methodology in studying philosophy. Philosophy is about analyzing and constructing arguments and a good understanding of the basics of logical reasoning is essential in performing that task. The next 3 lessons will focus on logic and analyzing arguments. In this lesson, you will first be introduced to the laws of logic. These are the first principles for all reasoning. We will then discuss the specialized terminology we use in logic. Finally, we will examine 2 major kinds of logical reasoning: deductive and inductive. We will consider different forms of arguments under each and discuss how to evaluate ...view middle of the document...
There is tertian guid. No such thing as “half-existing.”
3. The Law of Identity: “Something is what it is.” P = P. Clark Kent and Superman are two names for the same individual. Clark Kent is Superman and Superman is Clark Kent.
* Know the symbolic expression of the law of non-contradiction and how it clears up confusions.
Expressed symbolically is: ~ (P • ~P). ~ means “not” or “non” and negates any term or proposition that follows it. The parenthesis means “both.” The • means “and.” The P is a variable and can stand for any term or proposition. It should be read: “It is not the case that there can be both P and non-P.” Example: The logical opposite of black is not white, but rather “non-black,” which includes all colors (including grey).
* Explain the common confusion concerning God and contradictions.
Many people turn to the verse that says “with God all things are possible.” (Matthew 19:26) but this is taken out of context. When Jesus said this, He was talking about how difficult it is for rich people to be saved because they would rather cling to money than trust God. His point is that no man can save himself—only God can save us. When He says “all things,” He means all things that can possibly be – this does not include contradictions. God cannot be God and also not God at the same time. That is impossible.
* Know the symbolic expression of the Law of Excluded Middle. Why is it called the Law of Excluded Middle?
P v ~P. The “v” in the formula, called a wedge, means “either/or.” So the formula reads “Either P or non-P.”
* Know the why the laws of logic are self-evident.
They are self-evident and undeniable. By self-evident is meant they prove themselves and do not need any proof outside of themselves. Undeniable mean that the laws cannot be meaningfully denied. Any person denying these laws has to use them as the basis for the denial.
* Know the three parts of an argument.
1. Premises: also called reasons
2. Conclusion: trying to prove one of the other propositions
3. Inference: The relationship between the premises and the conclusion.
These relationships are described with metaphors. The premises lead to the conclusion or that the conclusion follows from the argument.
John Adams was the second president of the United States.
The square root of 81 is 9.
Therefore, I love pizza.
In this argument we have two premises and a conclusion but there is no inference between them. An argument put forth in which there is no inference is called anon sequitur which means “it does not follow.”
* Distinguish the language of evaluating arguments (deductive and inductive) from how we evaluate propositions.
Deductive arguments are evaluated as either valid or invalid. Inductive arguments are either strong or weak.
* Explain the relationship between truth value of the propositions with the validity/strength of the argument.
The truth value of the propositions in an argument has nothing to do...