11 We believe then In One God the Father the Unsearchable and Ineffable, Whom no man has seen, but the Only-begotten alone has declared Him. For He which is of God, He has seen God: whose face the Angels do always behold in heaven, behold, however, each according to the measure of his own rank. But the undimmed vision of the Father is reserved in its purity for the Son with the Holy Ghost.
Source: Catechetical Lectures (New Advent)