ἀνάγκᾳ δ' οὐδὲ θεοὶ μάχονται → but not even gods fight necessity (Simonides, fr. 37.1.29)
opinion: P. and V. δόξα, ἡ.
supposition: P. ὑπόθεσις, ἡ.
theory as opposed to practice: P. γνῶσις, ἡ (Plato, Politicus 259E).
science: P. and V. ἐπιστήμη, ἡ.