I come now to our second question: Does introspection give us materials
for the knowledge of relations other than those arrived at by reflecting
upon external perception? It might be contended that the essence of what
is "mental" consists of relations, such as knowing for example, and that
our knowledge concerning these essentially mental relations is entirely
derived from introspection. If "knowing" were an unanalysable relation,
this view would be incontrovertible, since clearly no such relation
forms part of the subject matter of physics. But it would seem that
"knowing" is really various relations, all of them complex. Therefore,
until they have been analysed, our present question must remain
unanswered I shall return to it at the end of the present course of
lectures.