It must be emphasized that a theology that is not the result of purification, that is, of ‘praxis’, is demonic. According to St. Maximus, “knowledge without praxis is the demons' theology”.
St. Thalassios, who had the same perspective, wrote that when man’s nous begins with simple faith, it “will eventually attain a theology that transcends the nous and that is characterized by unremitting faith of the highest type and the vision of the invisible”. Theology is beyond logic, it is a revelation of God to man, and the Fathers define it as theoria. Here too theology is chiefly vision of God. In another place the same Saint wrote that genuine love gives birth to spiritual knowledge, and “this is succeeded by the desire of all desires: the grace of theology”.
St. Diadochos of Photiki [teaches that] theology is the greatest gift offered to man by the Holy Spirit…. Therefore knowledge of God “comes through prayer, deep stillness and complete detachment, while wisdom comes through humble meditation on Holy Scripture and, above all, through grace given by God”. The gift of theology is a work of the Holy Spirit but in cooperation with man, since the Holy Spirit does not actualize in man a spiritual knowledge of the mysteries “apart from that faculty in him which naturally searches out such knowledge”.
…All these things show that theology is properly the fruit of man’s healing and not a rational discipline. Therefore in the Orthodox Patristic tradition theology is linked and identified with the spiritual father, and the spiritual father is the theologian par excellence – that is to say, the one who experiences the things of God and so can lead his spiritual children unerringly.
Father John Romanides writes: “The true Orthodox theologian is the one who has direct knowledge of some of God’s energies through illumination or knows them more through vision. Or he knows them indirectly through the prophets, apostles and saints or through scripture, the writings of the Fathers and the decisions and acts of their Ecumenical and Local Councils.
"Theology is not abstract knowedge or practice, like logic, mathematics, astronomy and chemistry, but on the contrary, it has a polemical character like logistics and medicine. The former is concerned with matters of defense and attack through bodily drill and strategies for the deployment of weapons, fortifications and defensive and offensive schemes, while the latter is fighting against mental and physical illnesses for the sake of health and the means of restoring health."
Metropolitan Hierotheos of Nafpaktos, Theology as a Therapeutic Science, pp. 33-36.