“18. The limits of our understanding
We must now explain what the power of human reason is, in regard to the kingdom of God, and spiritual discernments which consists chiefly of three things – the knowledge of God, the knowledge of his paternal favour towards us, which constitutes our salvation, and the method of regulating of our conduct in accordance with the Divine Law. With regard to the former two, but more properly the second, men otherwise the most ingenious are blinder than moles. I deny not, indeed, that in the writings of philosophers we meet occasionally with shrewd and apposite remarks on the nature of God, though they invariably savour somewhat of giddy imagination. As observed above, the Lord has bestowed on them some slight perception of his Godhead that they might not plead ignorance as an excuse for their impiety, and has, at times, instigated them to deliver some truths, the confession of which should be their own condemnation. Still, though seeing, they saw not. Their discernment was not such as to direct them to the truth, far less to enable them to attain it, but resembled that of the bewildered traveller, who sees the flash of lightning glance far and wide for a moment, and then vanish into the darkness of the night, before he can advance a single step. So far is such assistance from enabling him to find the right path. Besides, how many monstrous falsehoods intermingle with those minute particles of truth scattered up and down in their writings as if by chance. In short, not one of them even made the least approach to that assurance of the divine favour, without which the mind of man must ever remain a mere chaos of confusion. To the great truths, What God is in himself, and what he is in relation to us, human reason makes not the least approach.
19. Man’s spiritual blindness shown from John 1:4-5
But since we are intoxicated with a false opinion of our own discernment, and can scarcely be persuaded that in divine things it is altogether stupid and blind, I believe the best course will be to establish the fact, not by argument, but by Scripture. Most admirable to this effect is the passage which I lately quoted from John, when he says, “In him was life; and the life was the light of men. And the light shineth in darkness; and the darkness comprehended it not,” (John 1: 4, 5.) He intimates that the human soul is indeed irradiated with a beam of divine light, so that it is never left utterly devoid of some small flame, or rather spark, though not such as to enable it to comprehend God. And why so? Because its acuteness is, in reference to the knowledge of God, mere blindness. When the Spirit describes men under the term “darkness” he declares them void of all power of spiritual intelligence. For this reason, it is said that believers, in embracing Christ, are “born, not of blood, nor of the will of the flesh, nor of the will of man, but of God,” (John 1: 13;) in other words, that the flesh has no capacity for such sublime wisdom as to apprehend God, and the things of God, unless illumined by His Spirit. In like manner our Saviour, when he was acknowledged by Peter, declared that it was by special revelation from the Father, (Matthew. 16: 17.)”
-John Calvin, Institutes, Book 2, Chapter 2, parts 18 & 19