No one has yet discovered or ever shall discover what God is in His nature and essence... we shall, in time to come, 'know as we are known' (I Cor 13:12). But for the present what reaches us is a scant emanation, as it were a small beam from a great light - which means that any one who 'knew' God or whose 'knowledge' of Him has been attested to in the Bible, has a manifestly more brilliant knowledge than others not equally illuminated. This superiority was reckoned knowledge in the full sense, not because it really was so, but by the contrast of relative strengths.
Gregory of Nazianzus...God will be 'all in all' (I Cor. 15:28) when we are no longer what we are now, a multiplicity of impulses and emotions, with little or nothing of God in us, but are fully like God , with room for God and God alone. This is the 'maturity' (cf. Col. 1:28) towards which we speed.
Gregory of Nazianzus