Of God and His Creatures

If all things agreed in being -- and that the divine being -- all things would agree also in nature, since the being of God is simply identical with His nature. Agreeing at once in being and in nature, they would agree all over, all would be absolutely one, and one great and sole Reality would pervade and constitute the universe. To erect such a 'Reality,' or 'Idea,' or 'Absolute,' and then to proclaim it God, is pantheism. St Thomas argues that this all-pervading entity is not the universe, still less is it God: it has no concrete existence whatever: it is the shallowest, poorest and barest of the mind's creations, extending to and denoting everything, and therefore meaning and comprehending next to nothing. In its fourth canon, De Deo Creatore, the Vatican Council anathematises any who say that "God is a universal or indefinite being, which by self-determination constitutes the universe."

Of God and His Creatures: 1.26