g in general and terms to be related. For to perform a
synthesis is in general to relate, and the elements to be combined
are the terms to be related.[9] Now it is only necessary to take
instances to realize that the possibility of relating terms in certain
ways involves two presuppositions, which concern respectively the
general and the special nature of the terms to be related.

[9] 'To relate' is used rather than 'to recognize as
related', in order to conform to Kant's view of knowledge.
But if it be desired to take the argument which follows in
connexion with knowledge proper (cf. p. 242), it is only
necessary to substitute throughout 'to recognize as related'
for 'to relate' and to make the other changes consequent
thereon.

In the first place, it is clear that the general nature of the terms
must correspond with or be adapted to the general nature of the
relationship to be effected. Thus if two terms are to be related as
more or less loud, they must be sounds, since the relation in question
is one in respect of sound and not, e. g., of time or colour or space.
Similarly, terms to be related as right and left must be bodies in
space, right and left being a spatial relation. Again, only human
beings can be related as parent and child. Kant's doctrine, however,
does not conform to this presupposition. For the manifold to be
related consists solely of sensations, and of individual spaces, and
perhaps individual times, as elements of pure perception; and such a
manifold is not of the kind required. Possibly individual spaces may
be regarded as adequate terms to be related or combined into
geometrical figures, e. g. into lines or triangles. But a house as a
synthesis of a manifold cannot be a synthesis of spaces, or of times,
or of sensations. Its parts are bodies, which, whatever they may be,
are neither sensations nor spaces nor times, nor combinations of them.
In reality they are substances of a special kind. Again, the relation
of cause and effect is not a relation of sensations or spaces or
times, but of successive states of physical things or substances, the
relation consisting in the necessity of their succession.

In the second place, it is clear that the special nature of the
relation to be effected presupposes a special nature on the part of
the terms to be related. If one sound is to be related to another by
way of the octave, that other must be its octave. If one quantity is
t