ature which is the cause of awareness. The nature
which is the fact apprehended in awareness holds within it the greenness
of the trees, the song of the birds, the warmth of the sun, the hardness
of the chairs, and the feel of the velvet. The nature which is the cause
of awareness is the conjectured system of molecules and electrons which
so affects the mind as to produce the awareness of apparent nature. The
meeting point of these two natures is the mind, the causal nature being
influent and the apparent nature being effluent.

There are four questions which at once suggest themselves for discussion
in connexion with this bifurcation theory of nature. They concern (i)
causality, (ii) time, (iii) space, and (iv) delusions. These questions
are not really separable. They merely constitute four distinct starting
points from which to enter upon the discussion of the theory.

Causal nature is the influence on the mind which is the cause of the
effluence of apparent nature from the mind. This conception of causal
nature is not to be confused with the distinct conception of one part of
nature as being the cause of another part. For example, the burning of
the fire and the passage of heat from it through intervening space is
the cause of the body, its nerves and its brain, functioning in certain
ways. But this is not an action of nature on the mind. It is an
interaction within nature. The causation involved in this interaction is
causation in a different sense from the influence of this system of
bodily interactions within nature on the alien mind which thereupon
perceives redness and warmth.

The bifurcation theory is an attempt to exhibit natural science as an
investigation of the cause of the fact of knowledge. Namely, it is an
attempt to exhibit apparent nature as an effluent from the mind because
of causal nature. The whole notion is partly based on the implicit
assumption that the mind can only know that which it has itself produced
and retains in some sense within itself, though it requires an exterior
reason both as originating and as determining the character of its
activity. But in considering knowledge we should wipe out all these
spatial metaphors, such as 'within the mind' and 'without the mind.'
Knowledge is ultimate. There can be no explanation of the 'why' of
knowledge; we can only describe the 'what' of knowledge. Namely we can
analyse the content and its internal relations, but we cannot explain
why there is