unknowable is a castle in the air: how can we affirm that to be one of which we can know nothing? If it be really unknowable, we cannot possibly apply the category of number to it. This obscure basis can only afford an explanation of the harmony of the two worlds if we assume it to be possessed of a certain rationality; otherwise it might be revealed now in one way, now in another, the latter contradicting the former, and the thought-series might consequently develop along lines directly opposed to objective processes. Biehl may apparently succeed in proving the value of scientific concepts, but this is simply because he unconsciously transforms his unknowable into an essentially logical activity, to which he transfers the synthetic unity proper to our consciousness, and which he regards as a kind of potential thought.
9. Elimination of the Thing in Itself and Transition
to Phenomenalistic Monism. — In its final stage of development
critical philosophy, in order to shake off the fetters
of absurd agnosticism, has striven to eliminate the thing
in itself, and has turned towards that form of monism
prevalent in contemporary philosophy. The older form
of monism always took as its starting-point the duality
of subject and object, of internal and external experience,
and of the psychic and physical world, assuming it as
an undeniable fact, and then trying to reconcile the
opposition of the two regarded as originary empirical data,
by resorting to metaphysical speculation; it imagines,
that is to say, the existence over and above these two
orders of phenomena of a substance sustaining them both,
an entity which might be material or spiritual as best
suited the exigencies of the individual case, or which
might even, should it seem undesirable to define it too
sharply, be regarded as a tertium quid, neither matter
not spirit, unknowable in its essence and hence admirably
adapted to run with the hare and hunt with the hounds,
or act the part of a buffer state situated between two
belligerent powers. The new monism, on the contrary,
maintains the unity of the two orders of phenomena
