An Etymological Dictionary of Astronomy and Astrophysics

A kind of → deductive reasoning whereby from two initial → propositions (two → premises) a third related proposition (→ conclusion) is derived. The typical form of a → categorical syllogism is “A is B;” “C is A;” “Therefore, C is B.” For example,
“All humans are mortal.” “John is human.”
“Therefore, John is mortal.”

“Mortal” (B) is called the → major term; it occurs in the first premise and is the → predicate of the conclusion. “John” (C), the subject of the conclusion, is called the → minor term. “Human,” which is common to both premises and is excluded from the conclusion, is called the → middle term. See also → Aristotelian forms. Syllogism is purely formal. It does not enrich knowledge, but gives a new presentation to what is already known. It is also possible to have a logically valid syllogism based on → absurd premises. For example, “All cats are mammals.” “All cats are animals.” “Therefore, all animals are mammals.” Syllogism, representing the earliest branch of → formal logic, was developed in its original form by Aristotle in his Organon (Prior Analytics) about 350 BC.
See also:

→ bivalent logic, → polyvalent logic, → symbolic logic, → propositional logic, → first-order logic, → predicate logic, → syllogistic; → fuzzy logic.

Etymology (EN): M.E. silogisme, from O.Fr. silogisme, from L. syllogismus, from Gk. syllogismos “a syllogism,” originally “inference, conclusion; computation, calculation,” from syllogizesthai “bring together before the mind, compute, conclude,” from assimilated form of → syn- “together” + logizesthai “to reason, to count,” from logos “a reckoning, reason,” → logic.

Etymology (PE): Bâhamšomârik, literally “reckoning together,” from bâham “together,” from bâ “with,” → hypo-, + ham,
→ syn-, + šomâr present stem of šomârdan “to reckon, calculate, enumerate, account for,” → count, + suffix -i.