A syllogism (Greek: συλλογισμός — "conclusion," "inference"), (usually the categorical syllogism) is a kin 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.