Wiktionary
n. 1 inference in which the conclusion cannot be false given that the premises are true. 2 Inference in which the conclusion is of no greater generality than the premises.
WordNet
Wikipedia
Deductive reasoning, also deductive logic, logical deduction is the process of reasoning from one or more statements (premises) to reach a logically certain conclusion. It differs from inductive reasoning and 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 specific cases to general rules, i.e., there is epistemic uncertainty. However, the inductive reasoning mentioned here is not the same as induction used in mathematical proofs – mathematical induction is actually a form of deductive reasoning.
Usage examples of "deductive reasoning".
According to this wizard of deductive reasoning, the dead man’.
Let's take a page out of old-fashioned deductive reasoning, no computers, no technical analysis.
Using both inductive and deductive reasoning he would demonstrate an astounding verity, the kind of undislodgeable truth that would render absurd everything Billy had previously believed to be true.
It would be so much easier to just sweat a guy down than to do all this deductive reasoning.
In a lightning display of deductive reasoning that would have fascinated Tyber had he been aware of it, Zanita calculated her chances.
Turning on his emotion chip would put him in touch with those areas of deductive reasoning beyond mere logic, he reasoned, and it might also speed up his recovery.
I haven't much hope from it, but I thought I might try the deductive reasoning act for a change.
What is left, Watson, after all things impossible have been removed from the equation, will be only the possible as determined by the power of deductive reasoning.