8. It is noteworthy that this general knowledge is at times so recondite and delicate (especially when purer, simpler, and more perfect), spiritual and interior that the soul does not perceive or feel it even though the soul is employed with it. This is especially so when, as we affirmed, this knowledge is clearer, simpler and more perfect. And then this knowledge is still less perceptible when it shines on a purer soul, one freer from the particular ideas and concepts apprehensible by the sense or intellect. Since one lacks the feelings of the sensitive part of the soul, by not possessing these particular ideas and concepts that the sense and intellect are accustomed to act on, one does not perceive this knowledge.
For this reason the purer, simpler, and more perfect the general knowledge is, the darker it seems to be and the less the intellect perceives. On the other hand, the less pure and simple the knowledge is in itself, although it enlightens the intellect, the clearer and more important it appears to the individual, since it is clothed, wrapped, or commingled with some intelligible forms apprehensible to the intellect or the senses.
9. The following example is a clear illustration of this. In observing a ray of sunlight stream through the window, we notice that the more it is pervaded with particles of dust, the clearer and more palpable and sensible it appears to the senses. Yet obviously the sun ray in itself is less pure, clear, simple, and perfect in that it is full of so many specks of dust. We also notice that when it is more purified of these specks of dust it seems more obscure and impalpable to the material eye. And the purer it is, the more obscure and inapprehensible it seems to be. If the ray of sunlight should be entirely cleansed and purified of all dust particles, even the most minute, it would appear totally obscure and incomprehensible to the eye since visible things, the object of the sense of sight, would be absent. Thus the eye would find no images on which to rest, because light is not the proper object of sight but only the means by which visible things are seen. If there is nothing visible off which the ray of light can reflect, nothing will be seen. If the ray, then, were to enter through one window and go out another without striking any quantitative object, it would be invisible. Yet the ray of sunlight would be purer and cleaner than when it is more manifestly perceived because it is filled with visible objects.
10. The spiritual light has a similar relationship to the intellect, the eye of the soul. This supernatural general knowledge and light shines so purely and simply in the intellect and is so divested and freed of all intelligible forms (the objects of the intellect) that it is imperceptible to the soul. This knowledge, when purer, is even at times the cause of darkness because it dispossess the intellect of its customary lights, forms, and phantasies and effects a noticeable darkness.
When this divine light does not strike so forcibly, individuals apprehend neither darkness, nor light, nor anything at all from heavenly or earthly sources. Thus they sometimes remain in deep oblivion and afterward will not realize where they were, or what occurred, or how the time passed. As a result it can and does happen that a person will spend many hours in this oblivion, yet on returning to self think that only a moment or no time at all has passed.
– The Ascent of Mount Carmel, Book Two, Chapter 14, St. John of the Cross