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Deductive reasoning, also deductive logic, logical deduction or, informally, "top-down" logic,<ref>Deduction & Induction, Research Methods Knowledge Base</ref> is the process of reasoning from one or more statements (premises) to reach a logically certain conclusion.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> It differs from inductive reasoning or abductive reasoning.

Deductive reasoning 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 that hold over the entirety of a closed domain of discourse, narrowing the range under consideration until only the conclusion(s) is left. In inductive reasoning, the conclusion is reached by generalizing or extrapolating from, i.e., there is epistemic uncertainty. Note, however, that the inductive reasoning mentioned here is not the same as induction used in mathematical proofs – mathematical induction is actually a form of deductive reasoning.


Deductive reasoning sections
Intro  Simple example  Law of detachment  Law of Syllogism  Law of contrapositive  Validity and soundness   History   Education  See also  References  Further reading   External links   

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