BOOK I PART III
say, arises immediately, without any new op-
eration of the reason or imagination. Of this
I can be certain, because I never am conscious
of any such operation, and find nothing in the
subject, on which it can be founded. Now
as we call every thingcustom, which proceeds
from a past repetition, without any new rea-
soning or conclusion, we-may establish it as a
certain truth, that all the belief, which follows
upon any present impression, is derived solely
from that origin. When we are accustomed to
see two impressions conjoined together, the ap-
pearance or idea of the one immediately carries
us to the idea of the other.
Being fully satisfyed on this head, I make
a third set of experiments, in order to know,
whether any thing be requisite, beside the cus-
tomary transition, towards the production of