58. Varieties of the Categorical Syllogism. -- The categorical syllogism has for its premises two categorical propositions. It will be useful to note some of its possible structural modifications.

Such are the forms of reasoning called epicheireme, polysyllogism and sorites, enthymeme.

(1) The epicheireme (epi and cheirô to take in hand) now^{1} designates a syllogism one or both premises of which is immediately accompanied by the proof.

The polysyllogism is a series of syllogisms in which the conclusion of each serves as premise for the next. In practice the polysyllogism is condensed, under the form of sorites (sôros, heap), into a series of propositions where the predicate of the first becomes the subject of the second, and so on, in such a way that the predicate of the last in the series may he coupled with the first subject.

Example: The human soul forms abstract thoughts; a being capable of abstract thoughts is spiritual; a spiritual being is by nature imperishable; a being naturally imperishable cannot be annihilated; a spiritual being that cannot be annihilated will live with an immortal life; therefore the human soul is immortal.^{2}

{1} In Aristotle epicheireme means an attempt at demonstration as opposed to a demonstration properly so called.

{1} The enthymeme is commonly reckoned among the more or less disguised forms of the syllogism, as though it consisted merely in leaving one of the premises to be understood, not expressed. This is too secondary a circumstance to justify giving the enthymeme a place of its own among the forms of syllogism. As a matter of fact Aristotle understood by enthymeme a syllogism the conclusion of which is only more or less. probable.