Many believe that intellectual knowledge and understanding of a subject is not a sign of adepthood, etc., and I agree with that. After all, there are far too many armchair magicians out there, who, while I value their depth in intellectual knowledge, would perhaps benefit from even a minimum of a Qabalistic Cross in terms of practice. Knowledge is not power if it is not put to use. But some people seem to think that intellectual knowledge and understanding should be dispensed with entirely, that an adept can "go without", and I disagree with this. An adept should exlore both the theoretical and practical sides of magick. To stress one above the other is to create imbalance. Now, obviously some magicians are more scholarly than others, while some are better with energy work, clairvoyance, and so forth. We are each unique in our abilities, particularly in which ones are already developed and which ones develop more quickly than others. But that is no excuse for not attempting to balance things out. Both subjects should be approached with fervency and vigour. The student should try to amass an intuitive (Gnostic) understanding, as well as an intellectual one, and vice-versa if such should be the case. After all, what good can he or she be to anyone else if his or her experiences and intuitions cannot be expressed in a way understandable by the intellect of his or her brethren and sistern?
So, to point out the value of the intellect, let us explore some of the esoteric teachings on the matter. First there are the Gnostics, who held the Mind in high esteem. Mind was the pinnacle, not just distinguishing us from animals, but as the embodiment of Spirit. Mind is, in many esoteric circles, almost identical to Spirit. Teilhard de Chardin, while he would not have called himself a Gnostic, explores this idea in depth in his theories of the noosphere (nous is Greek for "mind").
In Hermetic philosophy we are thought that "All is Mind" (see the Kybalion, for example). The energy that exists throughout all levels of existence is mental. Now, while it can be argued that the mind is more than the intellect, the intellect is still part of the mind. Mind is magick. We use our mind to affect things, to cause changes in ourselves and our surroundings. The intellect is one of the keys to the mind.
The head is at the top of the pentagram. It is also up there near Kether. The Crown of God goes upon the head. Chokmah and Binah are often depicted as the two hemispheres of the brain. Resh, the letter of the Sun, means the Head. Qoph, the letter of the Moon, means the back of the head. This is the alchemical union of male and female, and it talks about the head, the house of the brain, which is the home of the intellect.
But the Qabalah goes one step further, for the three highest Sephiroth reference the head and mental faculties. We have Kether, the Crown, which goes on the head, as mentioned above. Then Chokmah is Wisdom. While we can argue what wisdom is, the ability to articulate the mysteries to others would be part of it, and this requires the intellect. Then we have Binah, which is Understanding, which is another mental faculty. If that were not enough, the "Sephirah which is not a Sephirah" of Da'ath, the Abyss, is Knowledge. Now, I, for example, would argue that this is Gnosis, which is experiential knowledge of the Divine (see here), not intellectual knowledge. But the fact remains that intellectual faculties are revered, utilised as symbols of the higher "intellect" of God, which goes beyond book knowledge.
Intellectual knowledge, understanding, and wisdom, is the earthly counterpart of the divine knowledge, understanding, and wisdom of Gnosis. As ever: As Above, So Below. To ignore the value of the intellect is to ignore the very real fact that it is a gift from God, who made us in his image, and has the potential to lead us back to Union with him.