The intellect perceives one light, and the senses another. The senses perceive sensible light, which manifests sensory things as sensory. The light of the intellect is the spiritual knowledge inherent in intellection. Thus sight and intellect do not perceive the same light, but each operates to the limit of its nature in what is natural to it.
When saintly people become the happy possessors of spiritual and supranatural grace and power, they see both with the sense of sight and with the intellect that which surpasses both sense and intellect in the manner that–to use the expression of St Gregory of Nazianzos–“God alone knows and those in whom these things are brought to pass”.
~St Gregory Palamas (Philokalia vol.4, p.424)
Prayerful Life 