Indeed, it is difficult to see how faith can be much strengthened in any other way. When we walk by faith, we walk, in a certain sense, in darkness. If it were perfectly light around us, we should not walk by faith, but by open vision. Faith is a light to the soul; but it is the very condition of its existence, that it shall have a dark place to shine in. It is faith which conducts us, but our journey is through shadows. And this illustrates the meaning of certain expressions frequently found in the experimental writings of Dionysius the Areopagite, and found also in other writers who hold similar views, such as the "night of faith," "the divine darkness," "the obscure night of faith," and the like.
It is hardly necessary to say, that darkness or night, in its application to the mind, is a figurative expression, and means trial or suffering, attended with ignorance of the issues and objects of that suffering. And, accordingly, these writers teach, in harmony with other experimental writers, that seasons of trial, leading to the exercise of faith, are exceedingly profitable. The biblical writers, whom they profess to follow, obviously teach the same. "Persecuted," says the apostle, "but not forsaken; cast down, but not destroyed. Always bearing about in the body the dying of the Lord Jesus, that the life also of Jesus might be made manifest in our body." And again, "Our light affliction, which is but for a moment, worketh for us a far more exceeding and eternal weight of glory." 2 Cor. 4:9, 10, 17.
— edited from A Treatise on Divine Union (1851) Part 5, Chapter 7.