The reason for which it is necessary for the soul, in order to attain to Divine union with God, to pass through this dark night of mortification of t… - John of the Cross

The breathing of the air, The song of the sweet nightingale, The grove and its beauty In the serene night, With the flame that consumes, and gives no pains. ~ 39

Meanwhile, God seeks to raise them higher, to draw them out of this miserable manner of loving to a higher state of the love of God, to deliver them from the low usage of the senses and meditation whereby they seek after God, as I said before,4 in ways so miserable and so unworthy of Him. He seeks to place them in the way of the spirit wherein they may the more abundantly, and more free from imperfections, commune with God now that they have been for some time tried in the way of goodness, persevering in meditation and prayer, and because of the sweetness they found therein have withdrawn their affections from the things of this world, and gained a certain spiritual strength in God, whereby they in some measure curb their love of the creature, and are able, for the love of God, to carry a slight burden of dryness, without going back to that more pleasant time when their spiritual exercises abounded in delights, and when the sun of the divine graces shone, as they think, more clearly upon them. God is now changing that light into darkness, and sealing up the door of the fountain of the sweet spiritual waters, which they tasted in God as often and as long as they wished. For when they were weak and tender, this door was then not shut, as it is written, “Behold, I have given before thee an opened door, which no man can shut; because thou hast a little strength, and hast kept My word, and hast not denied My name.”5 4. God thus leaves them in darkness so great

3. To prove the truth of the first reason, we take for granted a principle of the philosopher, namely, the more clear and evident divine things are, the more dark and hidden they are to the soul naturally. Thus the more clear the light the more does it blind the eyes of the owl,3 and the stronger the sun’s rays the more it blinds the visual organs; overcoming them, by reason of their weakness, and depriving them of the power of seeing. So the divine light of contemplation, when it beats on the soul, not yet perfectly enlightened, causes spiritual darkness, because it not only surpasses its strength, but because it blinds it and deprives it of its natural perceptions.