God prefers rather to incline the will than the intellect. Perfect clearness would be of use to the intellect, and would harm the will. To humble pride.

We make an idol of truth itself; for truth apart from charity is not God, but His image and idol, which we must neither love nor worship; and still less must we love or worship its opposite, namely, falsehood.

I can easily love total darkness; but if God keeps me in a state of semi-darkness, such partial darkness displeases me, and, because I do not see therein the advantage of total darkness, it is unpleasant to me. This is a fault, and a sign that I make for myself an idol of darkness, apart from the order of God. Now only His order must be worshipped.