BOOK I PART III
ciples, had they met with any satisfaction in
such as are clear and intelligible; especially in
such an affair as this, which must be an ob-
ject of the simplest understanding, if not of the
senses. Upon the whole, we may conclude, that
it is impossible in any one instance to shew the
principle, in which the force and agency of a
cause is placed; and that the most refined and
most vulgar understandings are equally at a
loss in this particular. If any one think proper
to refute this assertion, he need not put him-
self to the trouble of inventing any long reason-
ings: but may at once shew us an instance of a
cause, where we discover the power or oper-
ating principle. This defiance we are obliged
frequently to make use of, as being almost the
only means of proving a negative in philoso-
phy.