As we cannot come to Christ unless we are drawn by the Spirit, so when we are drawn we are lifted up in mind and heart above our understanding. For the soul, illumined by him, takes on a new keenness, as it were, to contemplate the heavenly mysteries, whose splendor had previously blinded it. And man’s understanding, thus beamed by the light of the Holy Spirit, then at last begins to taste those things which belong to the kingdom of God, having formerly been quite foolish and dull in tasting them…. Indeed, the Word of God is like the sun, shining upon all those to whom it is proclaimed, but with no effect among the blind. Now, all of us are blind by nature in this respect. Accordingly, it cannot penetrate into our minds unless the Spirit, as the inner teacher, through his illumination makes entry for it.
The Institutes of the Christian Religion Vol. 1 (Louisville, Kentucky; Westminster John Knox Press; 1974) p. 582.