its ingenious attempt to give to Kantism itself a consistency,
which, however, has only succeeded in producing a new
Lange.
philosophy of Neo-Kantism, differing from Kantism
in modifying the a priori and rejecting the thing
in itself. Lange to some extent modified the transcendentalism
of Kant’s theory of the origin of knowledge. A
priori forms, according to Kant, are contributions of the
mental powers of sense, understanding, and reason; but, according
to Lange, they are rooted in “the physico-psychical
organization.” This modification was the beginning of a gradual
lessening of the antithesis of a priori to a posteriori, until at
last the a priori forms of Kant have been transmuted into
“auxiliary conceptions,” or “postulates of experience.”
But this modification made no difference to the Kantian and
Neo-Kantian deduction from the epistemological to the
metaphysical. Lange entirely agreed with Kant that a priori forms
can have no validity beyond experience when he says: “Kant is
at any rate so far justified as the principle of intuition in space
and time a priori is in us, and it was a service to all time that he
should in this first great example, show that what we possess a
priori, just because it arises out of the disposition of our mind,
beyond our experience has no longer any claim to validity” (Hist.
of Materialism, trans. E. C. Thomas, ii. 203). Hence he deduced
that whatever we know from sensations arranged in such a priori
forms are objects of our own experience and mental phenomena.
Hence also his answer to materialism. Science, says the
materialist, proves that all known things are material phenomena.
Yes, rejoins Lange, but Kant has proved that material are merely
mental phenomena; so that the more the materialist proves his
case the more surely he is playing into the hands of the idealist—an
answer which would be complete if it did not turn on the
equivocation of the word “phenomenon,” which in science
means any positive fact, and not a mere appearance, much less a
mental appearance, to sense and sensory experience. Having,
however, made a deduction, which is at all events consistent,
that on Kantian assumptions all we know is mental phenomena,
Lange proceeded to reduce the rest of Kantism to consistency.
But his ardent love of consistency led him far away from Kant
in the end; for he proceeded consistently from the assumption,
that whatever we think beyond mental phenomena is ideal, to
the logical conclusion that in practical matters our moral responsibility
cannot prove the reality of a noumenal freedom, because,
as on Kant’s assumption we know ourselves from inner sense
only as phenomena, we can prove only our phenomenal freedom.
Lange thus transmuted inconsistent Kantism into a consistent
Neo-Kantism, consisting of these reformed positions: (1) we start
with sensations in a priori forms; (2) all things known from these
data are mental phenomena of experience; (3) everything beyond
is idea, without any corresponding reality being knowable.
“The intelligible world,” he concluded, “is a world of poetry.”
Our reflection is that there is a great difference between the
essence and the consistency of Kant’s philosophy. Its essence,
as stated by Kant, was to reduce the logical use of reason to
mental phenomena of experience in speculation, in order to
extend the practical use of reason to the real noumena, or things
in themselves, required for morality. Its consistency, as deduced
by Lange, was to reduce all use of reason, speculative and
practical, to its logical use of proceeding from the assumed mental
data of outer and inner sense, arranged a priori, to mental
phenomena of experience, beyond which we can conceive ideas
but postulate nothing. As H. Vaihinger, himself a profound
Kantian of the new school, says: “Critical scepticism is the
proper result of the Kantian theory of knowledge.”
There is only one Neo-Kantian way out of this dilemma, but it is to alter the original assumptions of Kant’s psychological idealism. This is the alternative of A. Riehl, who in Der philosophische Kriticismus (1876, &c.) proposes the non-Kantian hypothesis that, though things in themselves are unknowable through reason alone, they are knowable by empirical intuition, and Riehl. therefore also by empirical thought starting from intuition. Like all true followers of Kant, Riehl prefers epistemology to metaphysics; yet in reality he founds a metaphysics on epistemology, which he calls “critical realism,” so far as it asserts a knowledge of things beyond phenomena, and “critical monism,” so far as it holds that these things are unlike both physical and psychical phenomena, but are nevertheless the common basis of both. He accepts the Kantian positions that unity of consciousness combines sensations by a priori synthesis, and that therefore all that natural science knows about matter moving in space is merely phenomena of outer sense; and he agrees with Kant that from these data we could not infer things in themselves by reason. But his point is that the very sensation of phenomena or appearances implies the things which appear. Sensory knowledge, he says, “is the knowledge of the relations of things through the relations of the sensations of things.” Further, holding that, “like every other perception, the perception of a human body immediately involves the existence of that body,” and, like Fichte, believing in a “common consciousness,” he concludes that the evidence of sense is verified by “common consciousness” of the external world as objective in the Kantian sense of universally valid. He interprets the external world to be the common basis of physical and psychical phenomena. He rightly relies on the numerous passages, neglected by Lange, in which Kant regards things in themselves as neither phenomena nor ideas, but things existing beyond both. But his main reliance is on the passage in the Kritik, where Kant, speaking of the Cartesian difficulty of communication between body and soul, suggests that, however body and soul appear to be different in the phenomena of outer and inner sense, what lies as thing in itself at the basis of the phenomena of both may perhaps be not so heterogeneous (ungleichartig) after all. Riehl elaborates this bare suggestion into the metaphysical theory that the single basis of physical and psychical phenomena is neither bodily nor mental, nor yet space and motion. In order to establish this paradox of “critical monism,” he accepts to a certain extent the psychophysical philosophy of Fechner. He agrees with Fechner that physical process of nerve and psychical process of mind are really the same psychophysical process as appearing on the one hand to an observer and on the other hand to one’s own consciousness; and that physical phenomena only produce physical phenomena, so that those materialists and realists are wrong who say that physical stimuli produce sensations. But whereas Fechner and Paulsen hold that all physical processes are universally accompanied by psychical processes which are the real causes of psychical sensations, Riehl rejects this paradox of universal parallelism in order to fall into the equally paradoxical hypothesis that something or other, which is neither physical not psychical, causes both the physical phenomena of matter moving in space and the psychical phenomena of mind to arise in us as its common effects. In supposing a direct perception of such a nondescript thing, he shows to what straits idealists are driven in the endeavour to supplement Kant’s limitation of knowledge to phenomena by some sort of knowledge of things.
2. The Reaction to Hume.—When the Neo-Kantians, led by Lange, had modified Kant’s hypothesis of a priori forms, and retracted Kant’s admission and postulation of things in themselves beyond phenomena and ideas, and that too without proceeding further in the direction of Fichte and the noumenal idealists, there was not enough left of Kant to distinguish him essentially from Hume. For what does it matter to metaphysics whether by association sensations suggest ideas, and so give rise to ideas of substance and causation a posteriori, or synthetic unity of consciousness combines sensations by a priori notions of substance and causation into objects which are merely mental phenomena of experience, when it is at once allowed by the followers of Hume and Kant alike that reason in any logical use has no power of inferring things beyond the experience of the reasoner? In either case, the effective power of inference, which makes us rational beings, is gone. Naturally then the reaction to Kant was followed by a second reaction to Hume, partly under the name of “Positivism,” which has attracted a number of adherents, such as C. Göring (1841–1879), author of an incomplete System der Kritischen Philosophie (1874–1875) and E. Laas (q.v.), and partly under the name of the “physical phenomenology” of E. Mach.
Ernst Mach (q.v.) is a conspicuous instance of a confusion of physics and psychology ending in a scepticism like that of Hume. He tells us how from his youth he pursued physical and psychological studies, how at the age of fifteen he read Kant’s Prolegomena, and later rejected the thing in itself, and came to the conclusion that the world with his ego is one Mach. mass of sensations. For a time, under the influence of Fechner’s Psychophysics, he thought that Nature has two sides, a physical and a psychological, and added that all atoms have feeling. But in the progress of his physical work, which taught him, as he thought, to distinguish between what we see and what we
