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.