Emily Dickinson Lexicon

PRO'TA-SIS, n. [Gr. προτασις, from προτεινω, to present.]

1. A proposition; a maxim. – Johnson.
2. In the ancient drama, the first part of a comic or tragic piece, in which the several persons are shown, their characters intimated, and the subject proposed and entered on. The protasis might extend to two acts, where it ended, and the epitasis commenced. – Encyc.
3. The antecedent term of a proposition.