“… the noetic energy that functions in the heart of a person that is spiritually healthy.”
Originally, “nous” was understood by ancient (pre-Christian) Greek philosophers, most notably Plato and Aristotle, as man’s highest intellectual faculty. By intellectual faculty, the ancient Greeks did not mean the ability to reason things out to a logical conclusion, but rather the intuitive and immediate grasp of the reality of things. To them, “nous” was more of a direct contact between mind and truth.
The Church Fathers borrowed the term “nous” from Greek philosophy and gave it a distinctive Christian meaning. They used it to refer to the noetic energy that functions in the heart of a person that is spiritually healthy. The “nous” can be used to explain another borrowed concept from philosophy, the Logos Doctrine of the church. Second century Christian apologist Justin Martyr used the spermatikos logos (“seed” of the Word) to explain the universal indwelling presence of the Logos, the Word, or Son of God the Father within every human being (cf. the prologue to the Gospel of John, vv. 1:1-18). The idea of the “nous” also evolved over time among the Fathers. Early use of the term can be ambiguous as some early Fathers used the word “nous” when they were referring to the reasoning rational mind.
According to Orthodox theologian Fr. Michael Pomazansky (in his book, Orthodox Dogmatic Theology), it was the teaching of the overwhelming majority of the Church Fathers that the phrase ‘Image of God’ (cf. Genesis 1:26) refers to man’s soul, more precisely to the highest faculty of the soul, the “nous”. So, man is the “Image” by virtue of the spiritual nature of his “nous”. One common comparison made among patristic writers illustrates the relationship between body and the healthy “nous”. The analogy is that of the body being similar to a horse and the “nous” to the rider guiding and controlling the animal to move in the direction he would have it go.