“St. Dionysius and other mystic theologians call infused contemplation a ray of darkness, that is, for the unenlightened and unpurified soul, because this great supernatural light masters the natural power of the reason and takes away its natural way of understanding. Therefore, David also said: ‘Cloud and darkness are round about Him;’ not that this is so in reality, but in reference to our weak understanding, which, in light so great, becomes dimmed and blind, unable to ascend so high.... This is the reason why the illuminating ray of hidden wisdom, when God sends it from Himself into the soul not yet transformed, produces thick darkness in the understanding.”

In The Dark Night of the Soul, taking his position on the firm basis of the psychology and theology of St. Thomas Aquinas, and guiding himself by the light of Holy Scripture, St. John of the Cross pitilessly dissects the soul and its operations, separating not only what is dangerous or unsound, but everything that is not directly conducive to his ultimate aim, the union of the human will with the holy will of God.

A work of this magnitude must be begun by God, and accomplished by Him. The beginning consists in the grace of vocation, the end in the beatific vision. Between these two there lies a vast distance which it takes a lifetime to cover, where the generous and intelligent cooperation of the soul is indispensable.