Fr. Dimitru Staniloae writes,
Our thinking subject (our mind) is the highest sovereign which we encounter in the world; it raises itself over all the order of objects and avoids being grasped in any way. So it is the only entity which is like God. Therefore to raise ourselves in some way to an understanding of God, we must somehow understand the thinking subject in the created world.Here is a passage from Evagrius that many Fathers quote,
When the mind, unclothing itself of the old man, puts on that of grace, it sees in the time of prayer its state like that of a sapphire or of the heavenly color. This state Scripture calls the place of God, seen by the elders of Israel on Mt. Sinai.Fr. Dimitru tells us about the view of Saint Gregory of Nyssa
According to him, the cleansed heart sees God, not as a person apart, but he sees Him mirrored in himself. The heart or "the man within which the heart calls Lord" reflects God by its nature. But sin, covering it, has also covered the One mirrored in it. As soon as we cleanse it and it sees itself, it also sees God as some see the sun in a mirror, without turning to Him in order to see Him in His hypostasis.It is when the mind, purified, enters into this inner part of our being called the heart that it meets Christ. It here in this inner most chamber of our being that we experience an unlimitedness that cannot be captured by concepts and used by reason.
Fr, Dimitru says that in face of this new experience we are dumbfounded.
First, this dizziness or astonishment in the face of an abyss means a paralysis of the powers of the mind, to the extent that it can no longer move forward. The abyss in front of it is a great darkness. Secondly, it realizes that this abyss isn't entirely a region of our being, neither a void in the sense of an absence or a reality whatsoever. It isn't darkness strictly speaking. Rather it represents in continuity or by contact with the unlimitedness of our subject, the infinite depths. For us, it also represents the unlighted depths of divinity.When are able to enter into this abyss, where our mind seems to lose its boundaries, we, instead of feeling a void, begin to recognize the divinity in it. It is the condition of total apophaticism where we have abandoned not just the contents of our mind but also all of its content. This is the point where the Fathers tell us that we receive as a gift from God the vision of the divine light.
Fr. Dimitru tells us,
Arriving at our pure intimacy, we experience the infinite but personal presence of God hidden under the veil of the most complete darkness, just as many times we feel that somebody is near us, because we feel it, but we can't see anybody.This is the condition of pure prayer. With mental prayer we try to find, by using the name of Jesus, the place in our heart, or that center within us that is beyond reason. Our prayer seeks to find Jesus in this most inner place. Gradually, it becomes to know with certainty that it has met Jesus. (Don't be mistaken, this is not an image like we see on an icon, not an object of any kind, but is indescribable.) It is then, only through our inner prayer, that we experience God as subject and do not limit Him by any mental concepts. We become aware of our own nothingness and our dependence on God for our existence.
Fr. Dimitru says,
He penetrates into the content of our subject; He fills it and overwhelms us so much so that we forget ourselves.It up to us to continually knock at the door our the heart. We must continually try and open it. We have to make the knocking heard. This is the place were Christ dwells within each of us. He will open the door because we have purified ourselves and call out His name and show our need for Him.
Reference: Orthodox Spirituality, pp 286 -293