Lecture01

# Lecture01 - PHIL V3411 PHIL G4415 Introduction to Symbolic...

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PHIL V3411 / PHIL G4415 • Introduction to Symbolic Logic Lecture 1 Introduction and Overview

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INTRODUCTION TO SYMBOLIC LOGIC, LECTURE 1 P. 1 Introduction Logic is the study of arguments. An argument is a sequence of statements of which one is intended as a conclusion and the others, the premises , are intended to prove or at least provide good evidence for the conclusion. There are bad arguments as well as good ones. Examples: All humans are animals. } premises All animals are mortal. Therefore , all humans are mortal. conclusion All humans are animals. } premises Some animals are insects. Therefore , some humans are insects. conclusion Basic idea: an argument is good (or valid ) if it is not possible for its conclusion to be false when the premises are all true. (Intuitively: whoever accepts the premises of a valid argument must also accept the conclusion.) The purpose of logic is precisely to develop methods and techniques to tell good (i.e., valid) arguments from bad ones.
P. 2 More examples of arguments All humans are mortal. Socrates is human. Therefore , Socrates is mortal. 7 is a prime number. Therefore , there are prime numbers. If John went home, then Mary went to the movie. Mary didn’t go to the movie. Therefore , John did not go home. It’s either Monday, Tuesday, or Wednesday. It is not Monday. It is not Tuesday. Therefore , it is Wednesday. The premises and conclusion of an argument are declarative statements , i.e., assertions that are either true or false. So: No questions, exclamations, commands, etc.

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## This note was uploaded on 10/05/2008 for the course PHIL V3411 taught by Professor Varzi during the Spring '08 term at Columbia.

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Lecture01 - PHIL V3411 PHIL G4415 Introduction to Symbolic...

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