ἀλλὰ γάρ has a great variety of uses, most of which may be classed as follows:
a. In statements of direct opposition: καὶ ταῦτά σε πολλοῦ δεῖ λεληθέναι, ἀλλὰ γὰρ οἶμαι δ ἄρτι οὐκ ἔφησθα ποιεῖν, τοῦτο ποιεῖς
N. This use is post-Homeric, rare in the drama, common in the orators and Plato. It is especially frequent in putting and setting aside an objection supposed to be raised by an opponent (
b. In real and assumed objections (cp.
c. In transitions.—(1) At the close of the discussion of an argument, where the force of ἀλλά is like that of and yet or emphatic but. Thus, ἀλλὰ γάρ, ὦ
βουλή, ταῦτα μὲν ἐνθάδε οὐκ οἶδ' ὅ τι δεῖ λέγειν
ἀλλὰ γὰρ ἤδη ὥρα_ ἀπιέναι
(2) To restrain the expression of emotion; as ἀλλ' ἄναξ γάρ ἐστ' ἐμός, σι_γῶ
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].