Two kinds of faith exist: faith derived from hearing and learning, and faith derived from theoria. Although by no means separate from each other, these two kinds of faith are different from each other and naturally result in different kinds of knowledge of God. Faith derived from hearing and learning (simple faith) results in the natural knowledge of God: finding and learning about God through study, contemplating nature, accepting His revelation through Sacred Scripture, and various miracles/signs; what could be defined as exterior knowledge. Faith derived from theoria (perfect faith) results in the spiritual knowledge of God: acquiring and growing unceasingly in knowledge of Him and His mysteries, through communion and union with Him and the vision of the Divine Light; what could be defined as interior knowledge. Faith, especially faith derived from theoria, is closely linked with healing, for without the latter, “even demons have an external faith in God, including faith in the Holy Trinity” (Met. Hierotheos, The science of spiritual medicine, p. 72). Moreover, the progression from simple faith to perfect faith is dependent on the healing of the nous, the heart of the soul, through illumination.
Spiritual knowledge can be defined as that state of knowledge whereby one “sees invisibly, hears inaudibly and comprehends incomprehensibly for the glory of God” (Met. Hierotheos, The illness and cure of the soul, p. 193). Faith resulting from hearing and learning occurs both prior to and during purification, whereas faith resulting from theoria occurs after illumination of the nous, the heart of the soul, has occurred. Both the latter kind of faith and spiritual knowledge are what we are really called to enter into and fully achieve as Christians, because this is the beginning of deification: the true essence of why we have been created, the Incarnation, and the universal call to holiness (Lumen gentium) – “The Son of God became man so that man might become god” (St Athanasius, De inc. 54, 3: PG 25, 192B), and the hypostatic union occurred so that we may become “partakers of the divine nature” (2 P 1:4).