BOOK I PART III
ject to another. Without considering it in this
view, we can never arrive at the most distant
notion of it, or be able to attribute it either to
external or internal objects, to spirit or body, to
causes or effects.
The necessary connexion betwixt causes and
effects is the foundation of our inference from
one to the other. The foundation of our infer-
ence is the transition arising from the accus-
tomed union. These are, therefore, the same.
The idea of necessity arises from some im-
pression. There is no impression conveyed by
our senses, which can give rise to that idea. It
must, therefore, be derived from some internal
impression, or impression of reflection. There
is no internal impression, which has any rela-
tion to the present business, but that propen-
sity, which custom produces, to pass from an