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"Unless the heart be cleansed it is impossible to attain real contemplation. Only a heart purified of passion is capable of that peculiar awe and wonder before God which stills the nous into joyful silence." Archimandrite Sophrony
"The question of the vision of God, not only among Byzantine Theologians of the fourteenth century but also in earlier history, especially among the Greek Fathers, presents serious difficulty for those who want to study it from the standpoint of the concepts appropriate to Latin scholasticism." Vladimir Lossky The Vision of God p 20.
"It is necessary that whoever eagerly prosecutes the exercises of contemplation, first questions himself with particularity how much he loves. For the force of love is an engine of the soul, which while it draws it out of the world, lifts it on high." Saint Gregory the Great
"In this passing over (into God in a transport of contemplation), if it is to be perfect, all intellectual activities ought to be relinquished and the most profound affection transported to God, and transformed into him. This, however, is mystical and most secret, 'which no one knows except him who receives it', no one receives except him who desires it, and no one desires except him who is penetrated to the marrow by the fire of the Holy Spirit, whom Christ sent into the world." Saint Bonaventure
"I know that many persons who say vocal prayers are raised by God to high contemplation without their knowing how." Saint Teresa of Jesus
"There are three signs of inner recollection: first, a lack of satisfaction in passing things; second, a liking for solitude and silence, and an attentiveness to all that is more perfect; third, the considerations, meditations and acts that formerly helped the soul now hinder it, and it brings to prayer no other support than faith, hope, and love." Saint John of the Cross
- Eastern Orhtodox Christianity
Theoria appears in a variety of contexts.
- John Cassian
- "The Lord considered the chief good to reside in theoria alone – that is in divine contemplation." St. John Cassian 
- Metropolitan Hierotheos (Vlachos) of Nafpaktos
- "St. Maximus goes on to say that man is 'granted the grace of theology when, carried on wings of love' in theoria and 'with the help of the Holy Spirit, he discerns - as far as this is possible for the human nous - the qualities of God'."
- "St. Thalassios ... wrote that when man's nous begins with simple faith, it 'will eventually attain a theology that transcends the nous and that is characterised by unremitting faith of the highest type and the vision of the invisible'."
- "We accept faith by hearing it not so that we can understand it rationally, but that our hearts may be cleansed, that, by theoria, we may attain faith and ultimately experience the Revelation of God."
- "In the Holy Scripture it appears that faith comes by hearing the Word and by experiencing theoria (the vision of God)."
- "[T]he disciples of Christ acquired the knowledge of the Triune God in theoria (vision of God) and by revelation."
- "[T]heoria, vision and theosis are closely connected. Theoria has various degrees. There is illumination, vision of God, and constant vision (for hours, days, weeks, even months)."
- "They [Latins and Protestants] are influenced by the philosophical dialectic, which has been surpassed by the Revelation of God."
- The Roman Catholics as well do not have the perfection of the therapeutic tradition which the Orthodox Church has. Their doctrine of the filioque is a manifestation of the weakness in their theology to grasp the relationship existing between the person and society. They confuse the personal properties: the "unbegotten" of the Father, the "begotten" of the Son and the procession of the Holy Spirit. The Father is the cause of the "generation" of the Son and the procession of the Holy Spirit.
- "The Latins' weakness to comprehend and failure to express the dogma of the Trinity shows the non-existence of empirical theology. The three disciples of Christ (Peter, James and John) beheld the glory of Christ on Mount Tabor; they heard at once the voice of the Father: 'this is my beloved Son' and saw the coming of the Holy Spirit in a cloud -for, the cloud is the presence of the Holy Spirit, as St. Gregory Palamas says-. Thus the disciples of Christ acquired the knowledge of the Triune God in theoria (vision) and by revelation. It was revealed to them that God is one essence in three hypostases".
- "This is what St. Symeon the New Theologian teaches. In his poems he proclaims over and over that while beholding the uncreated Light, the deified man acquires the Revelation of God the Trinity. Being in 'theoria' (vision of God), the Saints do not confuse the hypostatic attributes. The fact that the Latin tradition came to the point of confusing these hypostatic attributes and teach that the Holy Spirit proceeds from the Son also, shows the non-existence of empirical theology for them. Latin tradition speaks also of created grace, a fact which suggests that there is no experience of the grace of God. For, when man obtains the experience of God, then he comes to understand well that this grace is uncreated. Without this experience there can be no genuine "therapeutic tradition".
- "St. Gregory the Theologian says that theoria and praxis are beneficial because theoria ... guides him to the holy of holies and restores him to his original nature; whereas praxis receives and serves Christ and tests love with actions. Clearly, theoria is the vision of God.... [P]raxis is whatever deeds it takes to lead to this love."
- Simeon the New Theologian
- 'He prays with his body alone, and not yet with spiritual knowledge. But when the man once blind received his sight and saw the Lord, he acknowledged Him no longer as the Son of David but as the Son of God, and worshipped Him' (John 9:38).
- Revelation 2:17
- Gleanings from Orthodox Christian Authors & the Holy Fathers - theoria. Orthodox.net. Retrieved on September 4, 2013.
- Conferences, I, chapter 8, translation by Boniface Ramsey
- Metropolitan Hierotheos of Nafpaktos, Christianity Is Not a Religion. It Is Psychotherapeutic Science
- Metropolitan Hierotheos Vlachos
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- Metropolitan Hierotheos of Nafpaktos2
- St Symeon the New Theologian, Philokalia, Vol.4, p. 17.