Of, relating to, or of the nature of an enthymeme; using compressed logical reasoning.
From enthymematic + -al, adding the -al suffix for a variant adjectival form. Medieval and Renaissance scholars preferred this longer -ical form for philosophical terms.
Notice how philosophy and logic texts used the -ical ending to sound more authoritative? It's the same reason we say 'methodical' rather than 'methodic'—extra syllables meant serious scholarship.
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