If by the term theology I understand the cognition of a primal being, that cognition is based either upon reason alone (theologia rationalis) or upon revelation (theologia revelata). The former cogitates its object either by means of pure transcendental conceptions, as an ens originarium, realissimum, ens entium, and is termed transcendental theology; or, by means of a conception derived from the nature of our own mind, as a supreme intelligence, and must then be entitled natural theology. The person who believes in a transcendental theology alone, is termed a deist; he who acknowledges the possibility of a natural theology also, a theist. The former admits that we can cognize by pure reason alone the existence of a Supreme Being, but at the same time maintains that our conception of this being is purely transcendental, and that all we can say of it is that it possesses all reality, without being able to define it more closely. The second asserts that reason is capable of presenting us, from the analogy with nature, with a more definite conception of this being, and that its operations, as the cause of all things, are the results of intelligence and free will. The former regards the Supreme Being as the cause of the world—whether by the necessity of his nature, or as a free agent, is left undetermined; the latter considers this being as the author of the world.
Transcendental theology aims either at inferring the existence of a Supreme Being from a general experience, without any closer reference to the world to which this experience belongs, and in this case it is called cosmotheology; or it endeavours to cognize the existence of such a being, through mere conceptions, without the aid of experience, and is then termed ontotheology.
Natural theology infers the attributes and the existence of an author of the world, from the constitution of, the order and unity observable in, the world, in which two modes of causality must be admitted to exist—those of nature and freedom. Thus it rises from this world to a supreme intelligence, either as the principle of all natural, or of all moral order and perfection. In the former case it is termed physico-theology, in the latter, ethical or moral-theology.[69]
[69] Not theological ethics; for this science contains ethical laws, which presuppose the existence of a Supreme Governor of the world; while moral-theology, on the contrary, is the expression of a conviction of the existence of a Supreme Being, founded upon ethical laws.
As we are wont to understand by the term God not merely an eternal nature, the operations of which are insensate and blind, but a Supreme Being, who is the free and intelligent author of all things, and as it is this latter view alone that can be of interest to humanity, we might, in strict rigour, deny to the deist any belief in God at all, and regard him merely as a maintainer of the existence of a primal being or thing—the supreme cause of all other things. But, as no one ought to be blamed, merely because he does not feel himself justified in maintaining a certain opinion, as if he altogether denied its truth and asserted the opposite, it is more correct—as it is less harsh—to say, the deist believes in a God, the theist in a living God (summa intelligentia). We shall now proceed to investigate the sources of all these attempts of reason to establish the existence of a Supreme Being.