Fr. Dimitru writes,
In negative theology we make an abstraction of the world only by reason and not totally even then, because when we negate one of God's attributes we think about what we negate.
So, negative theology is like a first step into this unknown space. At this stage we begin to realize the unknowability of God through reason. While we do so we realize the reality of His inner presence.
In mental prayer we turn away from all things and submerge ourselves in ourselves; we make an existential abstraction, total and lasting, by all that we are.
It is through mental prayer that we will make this final journey to be filled with the joy of the divine light and a higher knowledge of the divine though a union with God. There is a step beyond apophatic or negative theology which occurs through prayer. As we enter into mental prayer we enter into the depths of our inner being. We discover our true self and open the doors or our heart to knowledge of God.
In the prayer made in the heart we not only negate the world and think of it at the same time, but pure and simple we totally forget the world with our whole being. We are left only with ourselves and not with our superselves with our traits and properties which can be seen or thought about in definite concepts. Rather we remain with our "I" from the depths, unconstrained by the thought of things, which can't be seen or defined by any concept whatsoever. We find ourselves only with the simple consciousness of the presence of the self, of its indefinable realities.
As we enter the heart in prayer, which is the center of our being or our spirit, we leave the realm of concepts, reason and our normal mental processes. We now face the the pure self in its simplest form, free of mental concepts. What makes up our ego-self disappears. We are stripped or all the images we have created to make up our self-image. We are free and pure to face our Creator.
Saint Gregory Palamas says,
In prayer the mind gradually abandons all relations with created things: first with all things evil and bad, then with neutral things capable of conformity to either good or ill, according to the intentions of the person using them.
All the Holy Fathers tell us, according to Fr. Dimitru, that the absolutely essential condition to approach the mind of the infinite God is to leave behind all perceptible and intelligible things. This we are able to do, after preparation where we conquer our passions, in mental prayer.
Reference: Orthodox Spirituality, pp. 283-284