Since this is the proper moment, we ought to point out another benefit resulting from this night and dryness of the sensory appetite. So that the prophecy—your light will illumine the darkness (Is. 58:10)—may be verified, God will give illumination by bestowing on the soul not only knowledge of its own misery and lowliness but also knowledge of His grandeur and majesty.
When the sensory appetites, gratifications, and supports are quenched, the intellect is left clean and free to understand the truth, for even though these appetites and pleasures concern spiritual things, they blind and impede the spirit. Similarly, the anguish and dryness of the senses illumine and quicken the intellect, as Isaiah affirms: Vexation makes one understand (Is. 28:19). But God also, by means of this dark and dry night of contemplation, supernaturally instructs in His divine wisdom the soul that is empty and unhindered (which is the requirement for his divine inpouring), which He did not do through the former satisfactions and pleasures.
Isaiah explains this clearly: To whom will God teach his knowledge? And to whom will he explain his message? To them that are weaned, he says, from the milk, and to them who are drawn away from the breasts (Is. 28:9). This passage indicates that the preparation for this divine inpouring is not the former milk of spiritual sweetness or aid from the breast of the discursive meditations of the sensory faculties that the soul enjoyed, but the privation of one and a withdrawal from the other.
In order to hear God, people should stand firm and be detached in their sense life and affections, as the prophet himself declares: I will stand on my watch (with detached appetite) and will fix my foot (I will not meditate with the sensory faculties) in order to contemplate (understand) what God says to me (Heb. 2:1).
We conclude that self-knowledge flows first from this dry night and that from this knowledge as from its source proceeds the other knowledge of God. Hence St. Augustine said to God: “Let me know myself, Lord, and I will know you.” For as the philosophers say, one extreme is clearly known by the other.
Saint John of the Cross
The Dark Night: Book One, Chapter 12
John of the Cross, St. 1991, The Collected Works of St. John of the Cross, Revised Edition, translated from the Spanish by Kavanaugh, K and Rodriguez, O with revisions and introductions by Kavanaugh, K, ICS Publications, Washington DC.