Nous in Orthodox Christianity is the eye of the soul. Just as the soul of man, is created by God, man's soul is intelligent and noetic. St Thalassios wrote that God created beings "with a capacity to receive the Spirit and to attain knowledge of Himself; He has brought into existence the senses and sensory perception to serve such beings". Eastern Orthodox Christians hold that God did this by creating mankind with intelligence and noetic faculties. Angels have intelligence and nous, whereas men have reason, nous and sensory perception. This follows the idea that man is a microcosm and an expression of the whole creation or macrocosmos; it is through the healed and corrected nous and the intelligence that man knows and experiences God.
In this belief, soul is created in the image of God. Since God is Trinitarian, Mankind is Nous, Word and Spirit. The same is held true of the soul (or heart): it has nous, word and spirit. To understand this better first an understanding of St Gregory Palamas's teaching that man is a representation of the trinitarian mystery should be addressed. This holds that God is not meant in the sense that the Trinity should be understood anthropomorphically, but man is to be understood in a triune way. Or, that the Trinitarian God is not to be interpreted from the point of view of individual man, but man is interpreted on the basis of the Trinitarian God. And this interpretation is revelatory not merely psychological and human. This means that it is only when a person is within the revelation, as all the saints lived, that he can grasp this understanding completely (see theoria). The second presupposition is that mankind has and is composed of nous, word and spirit like the trinitarian mode of being. Man's nous, word and spirit are not hypostasis or individual existences or realities, but activities or energies of the soul. Were as in the case with God or the Persons of the Holy Trinity each are indeed hypostases. So these three components of each individual man are `inseparable from one another' but they do not have a personal character" when in speaking of the being that is mankind.
The nous as the eye of the soul, which some Fathers also call the heart, is the center of man and is where true (spiritual) knowledge is validated. This is seen as true knowledge which is "implanted in the nous as always co-existing with it".
- Orthodox Psychotherapy by Metropolitan Hierotheos Vlachos published by Birth of Theotokos Monastery,Greece (January 1, 2005) ISBN-13: 978-9607070272