Dr. Carus, as a positive monist, regards the problems of metaphysics as being like the mathematical surd,—not only irreducible but wholly irrational. He therefore declares it his ambition to eliminate from philosophy the "surd of metaphysics." He conducts his discussion under three heads: (1) The Elimination of the Metaphysical Surd from Philosophy; (2) The Metaphysical Residue in the Systems of Modern Thinkers; (3) The Soul as a Thing-in-itself.
The second division of his treatment is an exposition and criticism of the metaphysical conceptions of various representative thinkers, chiefly since the time of Comte, and really adds nothing to the understanding of the author's position. The other sections naturally concern the two grand divisions of metaphysical speculation, viz., the objective and subjective reality.
Like all the positivists, Dr. Carus seeks to solve the metaphysical problem by simply denying it. He even abrogates the 'Unknowable' of ordinary positivism, as being a metaphysical surd. Accordingly he limits knowledge to mere description and classification of experience, and, like Spencer, reduces the legitimate field of investigation to a philosophy of the sciences.
Although Dr. Carus's aim is to eliminate the metaphysical problem from speculation, nevertheless he appears to have actually reinstated it, simply in new dress, at every step of his discussion. For example, he opposes the dualism of Kant by positing a verbal monism, in which the subject and object are regarded as mere abstractions, "aspects" of one and the same reality. Both subject and object he regards as real, yet as to what the reality of "abstractions" or "aspects" consists in, we are not informed. Nor does he attempt to explain how one reality happens to have these two aspects. The dualism of Kant would appear to be more in harmony with empirical facts, to which positivism limits itself, than is the metaphysical "One" of Dr. Carus. When from the two "aspects" he goes back of empirical facts and hypothesizes only "one" reality, he thereby posits his "metaphysical surd" and so abandons his principle.
We have a unique contribution by Dr. Carus in his doctrine of "form," which, however, distinctly suggests Aristotle. Thus he holds that space, time, and all other forms in the objective world are not mere abstractions or mental contributions, but have reality in and of themselves. There are no things in themselves, but there are forms in themselves. In this manner he transposes into the objective world the formal categories of Kant, and hypostasizes them into realities. But how this is an improvement upon Kant is not manifest. His treatment of the soul is but a special application of his general principle. He defines soul as the "form" of the feelings; and mind forms are a "reflection" of the forms of objective existence. As
