Philosophy and Argumentation

What is Philosophy? Philosophical questions are general and fundamental. They arise from a critical examination of our ordinary beliefs. A philosophical belief is a general and fundamental belief that underlies many other ordinary beliefs. Philosophy attempts to determine if philosophical beliefs are true by examining whether they are based on good reasons. Philosophy tries to answer philosophical questions with rigorous argumentation. So logic is a crucial method of philosophy. Main Areas of Philosophy: • Epistemology: about the nature and scope of knowledge • Metaphysics: about the nature of reality and existence • Ethics / Moral Theory: about how we should act • Social and Political Philosophy: about how society should be organized Logic Logic is the study of argument form. An argument is a set of statements organized into one conclusion and one or more premises. The premises are supposed to support the conclusion. (Logic concerns the relationship between premises and conclusion, not the truth of premises.) In ordinary prose, terms like “therefore,” “consequently,” “so,” and “it follows that” indicate that a statement is a conclusion, while “since,” “for,” and “because” indicate that a statement is a premise. There are two major types of arguments: deductive and inductive: Deductive: Every mammal has a heart. All horses are mammals. ∴ Every horse has a heart. (The symbol ∴ stands for therefore.) Inductive: Every horse that has ever been observed has has a heart. ∴ Every horse has a heart. In an inductive argument the conclusion has information not contained in the premises, but the truth of the premises makes the truth of the conclusion only probable. In a deductive argument the truth of the premises guarantees the truth of the conclusion, but the conclusion has only information already contained in the premises. Good arguments: A valid argument is a good deductive argument: The truth of the premises guarantees the truth of the conclusion. (It is impossible for the conclusion to be false if all the premises are true.) A sound argument is also a good deductive argument: It is a valid argument with actually true premises. (The conclusion of a sound argument is always true.) Bad arguments: An invalid argument is a bad deductive argument: There is at least one case where the premises are all true and the conclusion is false. (It is possible for the conclusion to be false if all the premises are true.) Valid: All mammals are mortal. Invalid: All mammals are mortal. All dogs are mammals. All dogs are mortal. ∴ All dogs are mortal. ∴ All dogs are mammals. Common Argument Forms: Disjunctive Syllogism (VALID) Either P or Q Not Q ∴ P

Modus Ponens (VALID) Affirming the Consequent (INVALID) If P, then Q If P, then Q P Q ∴ Q ∴ P

Denying the Antecedent (INVALID) Modus Tollens (VALID) If P, then Q If P, then Q Not P Not Q ∴ Not Q ∴ Not P

The uppercase letters P and Q symbolize statements. You can replace them with any statement in the form and the validity or invalidity of the argument is preserved. Fallacies A fallacy is a bad argument, a mistake in reasoning, that may go unnoticed and it is tempting to make. There are two kinds of fallacy: formal and informal. Formal fallacies are arguments with incorrect logical forms: invalid arguments that people may feel tempted to take for valid. Affirming the consequent and denying the antecedent are good examples. Informal fallacies are mistakes in reasoning for reasons related to the content of the argument, rather than its logical form. Examples of Informal Fallacies: Circularity / Begging the Question Everything God says is true. The Bible is the word of God. So, everything the Bible says is true. The Bible says that God exists. ∴ God exists. Equivocation: If you don’t drink a lot in hot weather, you’ll become dehydrated. But if you drink a lot, you’ll become an alcoholic. ∴ In order to avoid dehydration, you must become an alcoholic.