syllogism

n. type of deductive reasoning containing two premises and a conclusion, logical argument in the form "if A=C and A=B then B=C" (Logic); deductive reasoning

A syllogism ( — "conclusion," "inference"), (usually the categorical syllogism) is a kind of logical argument in which one proposition (the conclusion) is inferred from two others (the premises) of a certain form. In Aristotle's Prior Analytics, he defines syllogism as "a discourse in which, certain things having been supposed, something different from the things supposed results of necessity because these things are so." (24b18–20) Despite this very general definition, he limits himself first to categorical syllogisms (and later to  modal syllogisms). The syllogism is at the core of deductive reasoning, where facts are determined by combining existing statements, in contrast to inductive reasoning where facts are determined by repeated observations.
See more at Wikipedia.org...

(n.)
The regular logical form of every argument, consisting of three propositions, of which the first two are called the premises, and the last, the conclusion. The conclusion necessarily follows from the premises; so that, if these are true, the conclusion must be true, and the argument amounts to demonstration
  

a model of reasoning introduced by Aristole.  The usual example is:
    All men are moral
    Socrates was a man
    Therefore, Socrates was moral.

Noun
1. deductive reasoning in which a conclusion is derived from two premises
(hypernym) deduction, deductive reasoning, synthesis
(part-meronym) conclusion, ratiocination
(derivation) syllogize, syllogise