ἀστεῖος: lit. ‘belonging to the town’ (Latin urbanus), so ‘polite’ (cp. English ‘urbane’), as opposed to ἄγροικος ‘belonging to the country’, so ‘rude’, ‘boorish’.
ταπεινούς, ‘too humble’, ‘abject’. ταπεινός is used generally in a bad sense in Classical Greek; contrast its use as ‘humble’ in a good sense in the New Testament. Humility was not a Greek virtue.
δεῖ δὲ χρῆσθαι μὲν ἀμφοτέραις ταῖς ἰδέαις ταύταις κτἑ, ‘you must cultivate both these qualities, and avoid the disadvantage which attaches to each.’ ἰδέα, lit. ‘appearance’, ‘form’, so ‘kind’, ‘class’. Here ἰδέαι means ‘kinds (i.e. of behaviour)’, ‘qualities’; cp. § 48, and N. C. 30, 44 and E. 9, where εἶδος is used in the same way, πᾶσι τοῖς εἴδεσι (sc. κόσμων). In Plato ἰδέα means a ‘class’, ‘species’, under which individual examples are arranged, and in Aristotle the ‘general idea’ or ‘principle’ underlying such a classification.
προσοῦσαν: a favourite word of Isocr. See note on E. 46.