Logic
i.e. the study of argument and the use of reason
-- in other words, logic is the study of thinking
Logic:
• does not deal with all mental phenomena (learning, remembering, daydreaming, etc.), but only with that type of thinking called “reasoning.”
• differs from Psychology
Logic
• is not concerned with emotional states at all, or with the “inner processes” going on in the mind of the thinker.
Logic
• is concerned only with reasoning itself, and the formulation of rules that will help us determine if any particular piece of reasoning is logical; i.e. coherent and consistent.
The Structure of Argument
• The basic unit of logic is the proposition or statement, typically expressed in a declarative sentence:
e.g. “Smith loves Jones.”
“Socrates is mortal.”
The Structure of Argument
• The key characteristic of each proposition is that it can be either true or false, but not both.
e.g. Either “Socrates is a man”is true, or “Socrates is not aman” is true -- but not both.
The Structure of Argument
• The chief concern of logic is how the truth of some propositions (premises) is connected with the truth of another (the conclusion).
The Structure of Argument
For example:
All men are mortal. (premise)
Socrates is a man. (premise)
Socrates is mortal. (conclusion)
The Structure of Argument
• The pattern of logic that lets us connect these premises to arrive at the conclusion we call an inference.
The Structure of Argument
• Without this pattern of inference, we have merely a collection of disjointed propositions.
e.g.“My dog has fleas.”
“The moon is made of cheese.”“Strawberries are red.”
The Structure of Argument
• Our primary concern is to evaluate the reliability of inferences, the patterns of reasoning that lead from premises to conclusion in a valid argument.