Philo Judaeus De Abrahamo 122

[122] Therefore, the middle person of the three, being attended by each of his powers as by body-guards, presents to the mind, which is endowed with the faculty of sight, a vision at one time of one being, and at another time of three; of one when the soul being completely purified, and having surmounted not only the multitudes of numbers, but also the number two, which is the neighbour of the unit, hastens onward to that idea which is devoid of all mixture, free from all combination, and by itself in need of nothing else whatever; and of three, when, not being as yet made perfect as to the important virtues, it is still seeking for initiation in those of less consequence, and is not able to attain to a comprehension of the living God by its own unassisted faculties without the aid of something else, but can only do so by judging of his deeds, whether as creator or as governor.