The beatific vision is the direct and unmediated vision of God held, in Catholic and much Western Christian theology, to be the final happiness of the blessed. Its texts pull in two directions, and its entire history is an attempt to hold them together. On one side: "now we see through a glass, darkly; but then face to face" (1 Corinthians 13:12); "we shall see him as he is" (1 John 3:2); "blessed are the pure in heart, for they shall see God" (Matthew 5:8). On the other: "no one has seen God at any time" (John 1:18), and God's word to Moses, "you cannot see my face, for no one shall see me and live" (Exodus 33:20).
Western scholasticism resolved the tension by holding that the blessed do see the divine essence itself, elevated to do so by a supernatural gift called the light of glory; Aquinas argued that nothing less could satisfy the intellect's natural desire to know the cause of what it knows, and that the vision is therefore the only possible final end of a rational creature. Benedict XII's constitution Benedictus Deus (1336) defined that the souls of the blessed see the divine essence immediately, and see it before the resurrection of the body, settling a controversy his predecessor John XXII had caused by preaching the opposite.
Eastern Orthodoxy took the other road. Following Gregory Palamas and the outcome of the fourteenth-century hesychast controversy, it holds that the divine essence remains forever unknowable and unparticipated, and that what is seen and shared is the uncreated energies, the light the disciples saw on Mount Tabor. To Palamas the Western position looked like a claim to comprehend the incomprehensible; to Western scholastics the Eastern position looked like a division introduced into a simple God. The disagreement is genuine, it is not merely verbal, and it resurfaces whenever the two traditions discuss deification.
Protestant theology has generally retained the hope of seeing God while giving much less weight to the scholastic apparatus, often preferring the language of communion, or of knowing God in Christ, to that of vision of the essence. Islamic theology ran a strikingly parallel dispute over ru'yat Allah, the vision of God in the hereafter: affirmed by Ash'ari and traditionist theology on the strength of "faces that day will be radiant, looking at their Lord" (75:22-23), and denied by the Mu'tazila and by Twelver Shia theology on the ground that to be seen is to be located and bounded, which God is not.