free will
From LSJ
ἄμεινον γὰρ ἑαυτῷ φυλάττειν τὴν ἐλευθερίαν τοῦ ἑτέρων ἀφαιρεῖσθαι → for it is better to guard one's own freedom than to deprive another of his
subs.
Of one's own free will: use adj., P. and V. ἑκών, αὐτεπάγγελτος, ἐθελοντής (Soph., Aj. 24), P. ἑκών γε εἶναι.