  In his natural theology, Rosmini offers considerations which are consistent with the basic principles of his philosophical teaching. Although he does not deny the validity of a posteriori proofs of the existence of God, he affirms that an a priori method is more satisfactory because it sets off from the idea of being, the foundation of his philosophy, and argues to the necessity of God’s existence. First, however, he posits a fundamental barrier to the perception of God at a purely natural level of human nature. For Rosmini, what is real can only be perceived through feeling, which indeed is part of human existence but only at a finite level where it cannot be the vehicle of the perception of God’s infinite reality. Ideal being, however, while expressing only the possibility, not the reality of things, is shown on analysis to be characterised by necessity, eternity and immateriality, factors which are intrinsic marks of possibility. The idea of being, therefore, with its divine characteristics serves as a bridge between God and human beings, enabling us to posit proofs of God’s existence without our knowing him through perception, or real contact. One example of the a priori proofs may be given here. If infinite, intelligible being is present to the human mind—and Rosmini would maintain that it is—an infinite mind capable of giving this idea to humans must exist. But such a mind cannot not be God. In this and all similar proofs, there is a common mode of procedure. The existence of God is necessary for the existence of intelligible being; but intelligible being certainly exists; the existence of God is therefore necessary. Having determined the existence of God, Rosmini then makes use of divinely revealed truth as a basis on which to offer some reflections about the nature of what he has proved to exist. These reflections, he would maintain, lie within the scope of philosophy because they depend methodologically solely on reason, and conclude with rational, not authoritative affirmations. Their basis in revelation, however, precludes any examination of them here.