What now is Spencer's theory of an ultimate reality that must for ever remain unknowable? Following a line of thought that had been steadily gaining ground since Hume—although much older than Hume—Spencer holds that in final analysis all our knowledge is a knowledge of mental states and their relations. Beyond this we know nothing, and can never know anything. Nevertheless, while we cannot know anything beyond consciousness, the conditions of thinking oblige us to assume that something exists as the cause of our states of mind. Just as black implies something that is not black, hard something that is not hard, so we must conceive, as against the conditioned, relative existence of our conscious states, an unconditioned, absolute existence as their cause. It is this assumed, but completely unknown cause of our conscious states, and of all else, that Spencer distinguishes as the Unknowable, the Unconditioned, the Absolute, etc., and which appears to have brought so much consolation to hard-pressed theists.
I have no intention of discussing here the philosophic value of the "Unknowable." But one may say, in passing, that even from that point of view Spencer is untrue to his own Agnosticism in speaking of the Unconditioned as the cause of phenomena. For causation is a category of the conditioned, it belongs to the world we know. It is not something that exists beyond consciousness, it is something that is supplied by consciousness and which possesses validity only within the world of phenomena. On Spencer's own theory of relativity a cause only exists in relation to an effect. Destroy the one and you destroy the other. Thus, if the Unknowable is a cause of phenomena it ceases to be the unconditioned and becomes part of the phenomenal order. If, on the other hand, it is not part of the phenomenal sequence, it cannot stand to phenomena in a genuine casual relation. It is, however, only fair to point out that between the Unknowable and the evolutionary philosophy of Spencer the only connection between them is that they are both in the same work. In all probability it is an unconscious survival of Spencer's earlier theism, which was active at the time the Synthetic Philosophy was originally planned, but which became more and more attenuated as Spencer grew older, and disappears entirely from the more important volumes of the series. And but for the help it has been supposed to give the belief in god, the "Unknowable" would only have ranked as a harmless speculation of no value to anyone or to anything. This is substantially admitted in a postscript to the 1899 edition of "First Principles." At the conclusion of the section entitled "The Unknowable," he says:—
The reader is not called on to judge respecting any of the arguments or conclusions contained in the foregoing five chapters and in the above paragraphs. The subjects on which we are about to enter are independent of the subjects thus far discussed; and he may reject any or all of that which has gone before while leaving himself free to accept any or all of that which is now to come.
In other words, the "Unknowable" is a pure abstraction, having no organic connection with the Synthetic Philosophy, or indeed with any philosophy of value. Mr. Spencer's warning to his readers seems to quite justify Mr. Bradley's rather caustic comment, "I do not wish to be irreverent, but Mr. Spencer's attitude towards his Unknowable strikes me as a pleasantry, the point of which lies in its unconsciousness. It seems a proposal to take something for God simply and solely because we do not know what the devil it can be." (Note to p. 128 of Appearance and Reality.)
The curious thing is that Mr. Spencer really offers his readers two theories of the nature of religion. One is contained in his "Principles of Sociology," and so far as it traces all religious ideas to the delusions and illusions of the primitive savage is substantially that held by all modern anthropologists. The other is contained in his "First Principles," and the two theories, like parallel lines, never meet. Though born in the same brain they are quite distinct, and even contradictory.
The substance of this second theory may be summarised as follows:—
1. The conditions of human thought compel the recognition of an unknowable reality of which all phenomena are the expression.
2. The function of religion, from the earliest time, has been the assertion of the existence of an unknowable reality, and to keep alive a consciousness of the insoluble mystery surrounding it.
3. The function of science is to deal with the known and the knowable, with all that is presented in experience, with the world of phenomena exclusively.
4. Religion having for its subject matter the unknown and unknowable, while science has for its subject matter the known and the knowable, religion and science are not antagonistic, but complementary. Conflicts only arise when one trespasses on the other's department, and a recognition of the true line of demarcation effectually reconciles these hitherto hostile forces.