ἀναγκαιότεραι μὲν οὖν πᾶσαι ταύτης, ἀμείνων δ᾽ οὐδεμία → accordingly, although all other sciences are more necessary than this, none is more excellent (Aristotle, Metaphysics A 983a10)
unyielding: P. ἰσχυρός, V. ἔμπεδος.
firm, secure: P. and V. βέβαιος.
persevering: P. and V. λιπαρής (Plato), Ar. γλίσχρος.
ceaseless: P. ἄπαυστος; see incessant.