CCC 1722 Such beatitude surpasses the understanding and powers of man. It comes from an entirely free gift of God: whence it is called supernatural, as is the grace that disposes man to enter into the divine joy.
“Blessed are the pure in heart, for they shall see God.” It is true, because of the greatness and inexpressible glory of God, that “man shall not see me and live,” for the Father cannot be grasped. But because of God’s love and goodness toward us, and because he can do all things, he goes so far as to grant those who love him the privilege of seeing him. .. For “what is impossible for men is possible for God.”1
1 St. Irenaeus, Adv. haeres. 4,20,5: PG 7/1, 1034-1035.