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.*
*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.
It may be sufficient in this place to define theoretical knowledge or cognition as knowledge of that which is, and practical knowledge as knowledge of that which ought to be. In this view, the theoretical employment of reason is that by which I cognize a priori (as necessary) that something is, while the practical is that by which I cognize a priori what ought to happen. Now, if it is an indubitably certain, though at the same time an entirely conditioned truth, that something is, or ought to happen, either a certain determinate condition of this truth is absolutely necessary, or such a condition may be arbitrarily presupposed. In the former case the condition is postulated (per thesin), in the latter supposed (per hypothesin). There are certain practical laws- those of morality- which are absolutely necessary. Now, if these laws necessarily presuppose the existence of some being, as the condition of the possibility of their obligatory power, this being must be postulated, because the conditioned, from which we reason to this determinate condition, is itself cognized a priori as absolutely necessary. We shall at some future time show that the moral laws not merely presuppose the existence of a Supreme Being, but also, as themselves absolutely necessary in a different relation, demand or postulate it- although only from a practical point of view. The discussion of this argument we postpone for the present.
When the question relates merely to that which is, not to that which ought to be, the conditioned which is presented in experience is always cogitated as contingent. For this reason its condition cannot be regarded as absolutely necessary, but merely as relatively necessary, or rather as needful; the condition is in itself and a priori a mere arbitrary presupposition in aid of the cognition, by reason, of the conditioned. If, then, we are to possess a theoretical cognition of the absolute necessity of a thing, we cannot attain to this cognition otherwise than a priori by means of conceptions; while it is impossible in this way to cognize the existence of a cause which bears any relation to an existence given in experience.
Theoretical cognition is speculative when it relates to an object or certain conceptions of an object which is not given and cannot be discovered by means of experience. It is opposed to the cognition of nature, which concerns only those objects or predicates which can be presented in a possible experience.
The principle that everything which happens (the empirically contingent) must have a cause, is a principle of the cognition of nature, but not of speculative cognition. For, if we change it into an abstract principle, and deprive it of its reference to experience and the empirical, we shall find that it cannot with justice be regarded any longer as a synthetical proposition, and that it is impossible to discover any mode of transition from that which exists to something entirely different- termed cause. Nay, more, the conception of a cause likewise that of the contingent- loses, in this speculative mode of employing it, all significance, for its objective reality and meaning are comprehensible from experience alone.
When from the existence of the universe and the things in it the existence of a cause of the universe is inferred, reason is proceeding not in the natural, but in the speculative method. For the principle of the former enounces, not that things themselves or substances, but only that which happens or their states- as empirically contingent, have a cause: the assertion that the existence of substance itself is contingent is not justified by experience, it is the assertion of a reason employing its principles in a speculative manner. If, again, I infer from the form of the universe, from the way in which all things are connected and act and react upon each other, the existence of a cause entirely distinct from the universe- this would again be a judgement of purely speculative reason; because the object in this case- the cause- can never be an object of possible experience. In both these cases the principle of causality, which is valid only in the field of experience- useless and even meaningless beyond this region, would be diverted from its proper destination.
Now I maintain that all attempts of reason to establish a theology by the aid of speculation alone are fruitless, that the principles of reason as applied to nature do not conduct us to any theological truths, and, consequently, that a rational theology can have no existence, unless it is founded upon the laws of morality. For all synthetical principles of the understanding are valid only as immanent in experience; while the cognition of a Supreme Being necessitates their being employed transcendentally, and of this the understanding is quite incapable. If the empirical law of causality is to conduct us to a Supreme Being, this being must belong to the chain of empirical objects- in which case it would be, like all phenomena, itself conditioned. If the possibility of passing the limits of experience be admitted, by means of the dynamical law of the relation of an effect to its cause, what kind of conception shall we obtain by this procedure? Certainly not the conception of a Supreme Being, because experience never presents us with the greatest of all possible effects, and it is only an effect of this character that could witness to the existence of a corresponding cause. If, for the purpose of fully satisfying the requirements of Reason, we recognize her right to assert the existence of a perfect and absolutely necessary being, this can be admitted only from favour, and cannot be regarded as the result or irresistible demonstration. The physico-theological proof may add weight to others- if other proofs there are- by connecting speculation with experience; but in itself it rather prepares the mind for theological cognition, and gives it a right and natural direction, than establishes a sure foundation for theology.
It is now perfectly evident that transcendental questions admit only of transcendental answers- those presented a priori by pure conceptions without the least empirical admixture. But the question in the present case is evidently synthetical- it aims at the extension of our cognition beyond the bounds of experience- it requires an assurance respecting the existence of a being corresponding with the idea in our minds, to which no experience can ever be adequate. Now it has been abundantly proved that all a priori synthetical cognition is possible only as the expression of the formal conditions of a possible experience; and that the validity of all principles depends upon their immanence in the field of experience, that is, their relation to objects of empirical cognition or phenomena. Thus all transcendental procedure in reference to speculative theology is without result.
If any one prefers doubting the conclusiveness of the proofs of our analytic to losing the persuasion of the validity of these old and time honoured arguments, he at least cannot decline answering the question- how he can pass the limits of all possible experience by the help of mere ideas. If he talks of new arguments, or of improvements upon old arguments, I request him to spare me. There is certainly no great choice in this sphere of discussion, as all speculative arguments must at last look for support to the ontological, and I have, therefore, very little to fear from the argumentative fecundity of the dogmatical defenders of a non-sensuous reason. Without looking upon myself as a remarkably combative person, I shall not decline the challenge to detect the fallacy and destroy the pretensions of every attempt of speculative theology. And yet the hope of better fortune never deserts those who are accustomed to the dogmatical mode of procedure. I shall, therefore, restrict myself to the simple and equitable demand that such reasoners will demonstrate, from the nature of the human mind as well as from that of the other sources of knowledge, how we are to proceed to extend our cognition completely a priori, and to carry it to that point where experience abandons us, and no means exist of guaranteeing the objective reality of our conceptions. In whatever way the understanding may have attained to a conception, the existence of the object of the conception cannot be discovered in it by analysis, because the cognition of the existence of the object depends upon the object's being posited and given in itself apart from the conception. But it is utterly impossible to go beyond our conception, without the aid of experience- which presents to the mind nothing but phenomena, or to attain by the help of mere conceptions to a conviction of the existence of new kinds of objects or supernatural beings.
But although pure speculative reason is far from sufficient to demonstrate the existence of a Supreme Being, it is of the highest utility in correcting our conception of this being- on the supposition that we can attain to the cognition of it by some other means- in making it consistent with itself and with all other conceptions of intelligible objects, clearing it from all that is incompatible with the conception of an ens summun, and eliminating from it all limitations or admixtures of empirical elements.
Transcendental theology is still therefore, notwithstanding its objective insufficiency, of importance in a negative respect; it is useful as a test of the procedure of reason when engaged with pure ideas, no other than a transcendental standard being in this case admissible. For if, from a practical point of view, the hypothesis of a Supreme and All-sufficient Being is to maintain its validity without opposition, it must be of the highest importance to define this conception in a correct and rigorous manner- as the transcendental conception of a necessary being, to eliminate all phenomenal elements (anthropomorphism in its most extended signification), and at the same time to overflow all contradictory assertions- be they atheistic, deistic, or anthropomorphic. This is of course very easy; as the same arguments which demonstrated the inability of human reason to affirm the existence of a Supreme Being must be alike sufficient to prove the invalidity of its denial. For it is impossible to gain from the pure speculation of reason demonstration that there exists no Supreme Being, as the ground of all that exists, or that this being possesses none of those properties which we regard as analogical with the dynamical qualities of a thinking being, or that, as the anthropomorphists would have us believe, it is subject to all the limitations which sensibility imposes upon those intelligences which exist in the world of experience.
A Supreme Being is, therefore, for the speculative reason, a mere ideal, though a faultless one- a conception which perfects and crowns the system of human cognition, but the objective reality of which can neither be proved nor disproved by pure reason. If this defect is ever supplied by a moral theology, the problematic transcendental theology which has preceded, will have been at least serviceable as demonstrating the mental necessity existing for the conception, by the complete determination of it which it has furnished, and the ceaseless testing of the conclusions of a reason often deceived by sense, and not always in harmony with its own ideas. The attributes of necessity, infinitude, unity, existence apart from the world (and not as a world soul), eternity (free from conditions of time), omnipresence (free from conditions of space), omnipotence, and others, are pure transcendental predicates; and thus the accurate conception of a Supreme Being, which every theology requires, is furnished by transcendental theology alone.