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1 Arguments 2 What is an Argument? • What does Monty Python have to say? • A philosophical argument is not a disagreement. • A philosophical argument is not a dispute. • A philosophical argument is not a quarrel. • A philosophical argument is not an opinion. Philosophical Arguments • A philosophical argument consists of one or more statements set out in support of some other statement. • Premises: the statements set out in support of some other statement. • Conclusion: the statement that other statements are set out to support. 3 Examples of Arguments All human beings are mortal. Socrates is a human being. Therefore, Socrates is mortal. Premises Conclusion Scrabble is not exciting, for Scrabble is safe, and nothing is both safe and exciting. Although all men are created equal, Batman is not equal to other men, because Batman is fictional, and fictional men are not the same as other men. 4 More Examples Poetry cannot be translated; and, therefore, it is the poets that preserve the languages; for we would not be at the trouble to learn a language if we could have all that is written in it just as well in a translation. But as the beauties of poetry cannot be preserved in any language except that in which it was originally written, we learn the language. -- Ben Johnson • Poetry cannot be translated. • We would not be at the trouble to learn a language if we could have all that is written in it just as well in a translation. • The beauties of poetry cannot be preserved in any language except that in which it was originally written. • Therefore, it is the poets that preserve the languages. 5 More Examples It is impossible to make people understand their ignorance; for it requires knowledge to perceive it and therefore he that can perceive it hath it not. -- Jeremy Taylor • Understanding ignorance requires knowledge to perceive it. • Therefore, he that can perceive ignorance hath it not. • Therefore, it is impossible to make people understand their ignorance. 6 More Examples? Man is the only animal that laughs and has a state legislature. -- Samuel Butler The statistics on sanity are that one out of every four Americans is suffering from some form of mental illness. Think of your three best friends. If they're okay, then it's you. -- Rita Mae Brown What if everything is an illusion and nothing exists? In that case, I definitely overpaid for my carpet. -- Woody Allen 7 Deductive and Inductive Arguments Deductive Arguments • Deductive arguments are arguments in which the conclusion is presented as following from the premises with necessity. Inductive Arguments • Inductive arguments are arguments in which the conclusion is presented as following from the premises with a high degree of probability. 8 Examples Deductive Argument: I own every Dario Argento film. Suspiria (1977) is a Dario Argento film. Therefore, I own a copy of Suspiria. Inductive Argument: Every Keanu Reeves movie I have seen is awful. The Night Watchman (2008) will be a Keanu Reeves movie. So The Night Watchman will be awful. 9 Logical Validity & Soundness in Deductive Arguments In constructing and evaluating arguments, we need to consider two things: • Are its premises true? • Does its conclusion follow necessarily from its premises? Philosophers use the answers to these questions to classify arguments. 10 Deductive Validity A deductive argument is valid just in case the truth of its premises would absolutely guarantee the truth of its conclusion. In other words, it is valid just in case there is no possible way the premises could all be true but the conclusion false. 11 Deductive Soundness A deductive argument is sound just in case it is valid and all of its premises are true. So an argument can only be sound if it is also valid. 12 Evaluating Arguments for Soundness & Validity Darren is taller than William. William is taller than Aaron. Therefore, Darren is taller than Aaron. To be a Canadian citizen, one has to be born in Canada. Darren was born in Canada. Therefore, Darren is a Canadian citizen. All cats chase mice. Tigers do not chase mice. Therefore, tigers are not cats. 13 More Arguments Everyone likes Phil140. All Phil140 exams are easy. Therefore, everyone will receive a high grade in Phil140. All books are printed in multiples of 16 pages. What’s Wrong? Has 746 pages. 746 is not divisible by 16. Therefore, What’s Wrong? is not a book. Some tests are multiple choice. Some exams are multiple choice. Therefore, some tests are exams. 14 Some Common Fallacies Equivocation In equivocation, the meaning of a key term shifts during the course of an argument. Man is the only rational creature. No woman is a man. Therefore, no woman is a rational creature. Any person with a handicap is at a disadvantage. Raymond has a golf handicap. Raymond is at a disadvantage in golf. 15 Some Common Fallacies Circularity In a circular argument, something (A) is asserted to be true just in case something else (B) is true. But B turns out to be true just in case A is true. The Bible is the infallible Word of God. The Bible says that God exists. Therefore, God exists. My essays always deserve at least a “B”. This is one of my essays. Therefore, this essay did not deserve a “C”. 16 Necessary & Sufficient Conditions Necessary Condition If A is a necessary condition for B, then if not-A then not-B. Sleeping is a necessary condition for dreaming. • If you are not sleeping, then you are not dreaming. Sufficient Condition If A is a sufficient condition for B, then if A, then B. Dreaming is a sufficient condition for sleeping. • If you are dreaming, then you are sleeping.