The proposition, that your action has such-and-such a
cause, is a hypothesis. The hypothesis is
well-founded if one has had a number of experiences which,
roughly speaking, agree in showing that your action is the regular
sequel of certain conditions which we then call causes of the
action. In order to know the reason which you had for
making a certain statement, for acting in a particular way,
etc
., no number of agreeing experiences is
necessary, and the statement of your reason is not a
hypothesis. The difference between the grammars of
“reason” and “cause” is quite
similar
24.
to that between the
grammars of “motive” and
“cause”. Of the cause one can say that
one can't
know it but one can only conjecture
it. On the other hand one often says:
“Surely
I must know why I did it”
talking of the
motive. When I say:
“we can only
conjecture the cause but we
know the motive” this statement will be seen
later on to be a grammatical one. The
“can” refers to a
logical
possibility.