BOOK I PART III
guished from experience, can never make us
conclude, that a cause or productive quality is
absolutely requisite to every beginning of ex-
istence. Both these considerations have been
sufficiently explained: and therefore shall not
at present be any farther insisted on.
I shall only infer from them, that since rea-
son can never give rise to the idea of efficacy,
that idea must be derived from experience, and
from some particular instances of this efficacy,
which make their passage into the mind by
the common channels of sensation or reflection.
Ideas always represent their objects or impres-
sions; and vice versa, there are some objects
necessary to give rise to every idea. If we pre-
tend, therefore, to have any just idea of this effi-
cacy, we must produce some instance, wherein
the efficacy is plainly discoverable to the mind,