Logic is not (as some erroneously believe) the science of thinking. The term “thinking” includes several operations of the human mind, many of which would fall under the domain of psychology rather than logic. But there are three mental operations which are usually associated with logic: apprehension, judgment, and reasoning.

Apprehension is the mental operation by which an idea is formed in the mind. If you were to think of a sunset or a baseball, the action of forming that picture in your mind is apprehension. The verbal expression of apprehension is called a term.

Judgment is the mental operation by which we predicate something of a subject. To think, “That sunset is beautiful” or “Baseball is the all-American sport” is to make a judgment. The verbal expression of judgment is the statement (or proposition).

Inference (or reasoning) is the mental operation by which we draw conclusions from other information. If you were to think, “I like that sunset, because I enjoy beautiful things, and that sunset is beautiful” you would be reasoning. The verbal expression of reasoning is the logical argument.

Formal logic is more properly defined as the science of reasoning. Students of formal logic analyze syllogisms to determine their validity, or develop proofs to establish a given conclusion. Logic students also learn how to define terms and make accurate statements, because these tools are necessary to learn in order to reason properly. But in so doing they are working more in the realm of informal logic, the branch of logic which is important, but which is only indirectly related to reasoning.