It is possible to demonstrate God's existence, although not a priori, yet a posteriori from some work of His more surely known to us.
Thomas AquinasI answer that, Even, as in the blessed in heaven there will be most perfect charity, so in the damned there will be the most perfect hate.
Thomas AquinasThat the saints may enjoy their beatitude and the grace of God more abundantly they are permitted to see the punishment of the damned in hell.
Thomas Aquinas