Do you now understand that in place of the intellect, the eyes and the ears, they acquire the incomprehensible Spirit and by Him hear, see and comprehand? For if all their intellectual activity has stopped, how could the angels and angelic men see God except by the power of the Spirit? This is why their vision is not a sensation, since they do not receive it through the senses; nor is it intellection, since they do not find it through thought or the knowledge that comes thereby, but after the cessation of all mental activity. It is not, therefore, the product of either imagination or reason; it is neither an opinion nor a conclusion reached by syllogistic argument.
On the other hand, the mind does not acquire it simply by elevating itself through negation. For, according to the teaching of the Fathers, every divine command and every sacred law has as its final limit purity of heart; every mode and aspect of prayer reaches its term in pure prayer; and every concept which strives from below towards the One Who transcends all and is separate from all comes to a halt once detached from all created beings. However, it is erroneous to say that over and above the accomplishment of the divine commands, there is nothing but purity of heart. There are other things, and many of them: There is the pledge of things promised in this life, and also the blessings of the life to come, which are rendered visible and accessible by this purity of heart. Thus, beyond prayer, there is the ineffable vision, and ecstasy in the vision, and the hidden mysteries. Similarly, beyond the stripping away of beings, or rather after the cessation [of our perceiving or thinking of them] accomplished not only in words, but in reality, there remains an unknowing which is beyond knowledge; though indeed a darkness, it is yet beyond radiance, and, as the great Denys says, it is in this dazzling darkness that the divine things are given to the saints.
Thus the perfect contemplation of God and divine things is not simply an abstraction; but beyong this abstraction, there is a participation of divine things, a gift and a possession rather than just a process of negation. But these possessions and gifts are ineffable: If one speaks of them, one must have recourse to images and analogies—not because that is the way in which these things are seen, but because one cannot adumbrate what one has seen in any other way. Those, therefore, who do not listen in a reverent spirit to what is said about these ineffable things, which are necessarily expressed through images, regard the knowledge that is beyond wisdom as foolishness; trampling under foot the intelligible pearls, they strive also to destroy as far as possible by their disputation those who have shown them to them.
St Gregory Palamas. The Triads I.iii.18