|St. John of the Cross|
"Into this dark night souls begin to enter when God draws them forth from the state of beginners—which is the state of those that meditate on the spiritual road—and begins to set them in the state of progressives—which is that of those who are already contemplatives—to the end that, after passing through it, they may arrive at the state of the perfect, which is that of the Divine union of the soul with God. Wherefore, to the end that we may the better understand and explain what night is this through which the soul passes, and for what cause God sets it therein..."
(Chapter 1 of "The Dark Night of the Soul")