…the preparation of the soul for this union, as we said, is not that it should understand or perceive or feel or imagine anything, concerning either God or aught else, but that it should have purity and love — that is, perfect resignation and detachment from everything for God’s sake alone; and, as there can be no perfect transformation if there be not perfect purity, and as the enlightenment, illumination and union of the soul with God will be according to the proportion of its purity, in greater or in less degree; yet the soul will not be perfect, as I say, if it be not wholly and perfectly bright and clean.
– St. John of the Cross