-- in other words, logic is i.e. the study of argument and the use of reason -- in other words, logic is the study of thinking

Logic: differs from Psychology does not deal with all mental phenomena (learning, remembering, daydreaming, etc.), but only with that type of thinking called “reasoning.”

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 a man” 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.