t 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
