but are perfectly unintelligible and inexplicable.  For it is evident philosophers would never have had recourse to such obscure and uncertain principles, had they met with any satisfaction in such as are clear and intelligible; especially in such an affair as this, which must be an object 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 himself to the trouble of inventing any long reasonings:  but may at once shew us an instance of a cause, where we discover the power or operating principle.  This defiance we are obliged frequently to make use of, as being almost the only means of proving a negative in philosophy.

The small success, which has been met with in all the attempts to fix this power, has at last obliged philosophers to conclude, that the ultimate force and efficacy of nature is perfectly unknown to us, and that it is in vain we search for it in all the known qualities of matter.  In this opinion they are almost unanimous; and it is only in the inference they draw from it, that they discover any difference in their sentiments.  For some of them, as the Cartesians in particular, having established it as a principle, that we are perfectly acquainted with the essence of matter, have very naturally inferred, that it is endowed with no efficacy, and that it is impossible for it of itself to communicate motion, or produce any of those effects, which we ascribe to it.  As the essence of matter consists in extension, and as extension implies not actual motion, but only mobility; they conclude, that the energy, which produces the motion, cannot lie in the extension.

This conclusion leads them into another, which they regard as perfectly unavoidable.  Matter, say they, is in itself entirely unactive, and deprived of any power, by which it may produce, or continue, or communicate motion:  But since these effects are evident to our senses, and since the power, that produces them, must be placed somewhere, it must lie in the deity, or that divine being, who contains in his nature all excellency and perfection.  It is the deity, therefore, who is the prime mover of the universe, and who not only first created matter, and gave it it’s original impulse, but likewise by a continued exertion of omnipotence, supports its existence, and successively bestows on it all those motions, and configurations, and qualities, with which it is endowed.