According to our logic, the universe is the truth and everything partakes of it. That such a truth is logical and such a logic true, is shown by the interconnection of things, so that this science is applicable to everything which the sciences respect as reasonable and true.
In order to help you in the understanding of the absolute and liberate your thought from all special miracles, I refer to Kant's critique of reason. It teaches that our intellect becomes a source of understanding only in connection with other phenomena of nature. Only his critique stuck fast in the mysterious fountain of causality. Thus he showed that he was only a seeker after logic, not its master. The conclusion that there must be something that does appear where there are phenomena is certainly correct. But that which Kant was thinking of, something of a transcendental or metaphysical nature, led him to the radically wrong conclusion that there must be something different, peculiar, miraculous, mysterious, wherever there are phenomena.
The Kantian conclusion that there must be an absolute truth by itself behind a phenomenon, an absolute truth that exists independent of and disconnected with such phenomenon, was due to his fetish-like conception of truth. It is the first requirement for a correct use of the faculty of logical reasoning to know that truth is the common nature of the universe.
That a phenomenon must be based on nature, or an effect on a cause, is a fact identical with "causality" which I already promised to discuss in the preceding letter. This same problem may also be expressed in the words: Where there are predicates, there must be a subject that carries them. In order to make quite sure that I will not be misunderstood, I emphasize once more the fact that I am not raising any doubt as to the correctness of this conclusion, but only to the metaphysical application of this conclusion after the Kantian manner which consists in making the same use of it as a clergyman who tries to prove that his theology is innate in reason.
Our conception of logic wishes to show that all causes and effects are matter of the same kind, and that our faculty of reasoning is a matter of fact thing which brooks no mysteries or metaphysical dreams.
SIXTEENTH LETTER
Now let me illustrate the interconnection of all things, or the world-unit, by discussing the question of causality. We know that everything has its cause. We know that this is also true on the Moon or on Uranus, although we have not acquired this knowledge by experience on those world bodies. Thus it seemed that the intellect was a mysterious receptacle containing innate wisdom. The same receptacle also contains, for instance, the truth that all white horses are white and all black horses black. We do not know anything about the color of other horses in other countries, but the color of black and white horses we know even if we have never seen them in other countries. It is thus apparent that our intellect is an instrument which reaches beyond experience. For this reason there would seem to be no telling where the supply of such miraculous revelations would stop and into what mysterious worlds the intellect passing beyond the limits of experience would lead us.
In order that the human intellect may not appear transcendental, in order to give it its place in the general classification of natural forces, we must investigate the nature of causality and so-called a priori knowledge.