Deductive reasoning Deductive reasoning Deductive reasoning, also deductive logic, logical deduction is the process of reasoning from one or more statements (premises) to reach a logically certain conclusion. Deductive reasoning goes in the same direction as that of the conditionals, and links premises with conclusions. If all premises are true, the terms are clear, and the rules of deductive logic are followed, then the conclusion reached is necessarily true. Deductive reasoning (""top-down logic"") contrasts with inductive reasoning (""bottom-up logic"") in the following way; in deductive reasoning, a conclusion is reached reductively by applying general rules which hold over the entirety of a
Logical disjunction to but different from the logical "or". For example, "Please ring me or send an email" likely means "do one or the other, but not both". On the other hand, "Her grades are so good that either she's very bright or she studies hard" does not exclude the possibility of both. In other words, in ordinary language "or" (even if used with "either") can mean either the inclusive "or" [inclusive-]or the exclusive "or." Logical disjunction In logic and mathematics, or is the truth-functional operator of (inclusive) disjunction, also known as alternation; the "or" of a set of operands is true