If we pretend, therefore, to have any just idea of this efficacy, we must produce some instance, wherein the efficacy is plainly discoverable to the mind, and its operations obvious to our consciousness or sensation.
By the refusal of this, we acknowledge, that the idea is impossible and imaginary, since the principle of innate ideas, which alone can save us from this dilemma, has been already refuted, and is now almost universally rejected in the learned world.

Our present business, then, must be to find some natural production, where the operation and efficacy of a cause can be clearly conceived and comprehended by the mind, without any danger of obscurity or mistake.
In this research we meet with very little encouragement from that prodigious diversity, which is found in the opinions of those philosophers, who have pretended to explain the secret force and energy of causes.

[See Father Malbranche, Book vi.

Part 2, chap.3.And the illustrations upon it.] There are some, who maintain, that bodies operate by their substantial form; others, by their accidents or qualities; several, by their matter and form; some, by their form and accidents; others, by certain virtues and faculties distinct from all this.

All these sentiments again are mixed and varyed in a thousand different ways; and form a strong presumption, that none of them have any solidity or evidence, and that the supposition of an efficacy in any of the known qualities of matter is entirely without foundation.
This presumption must encrease upon us, when we consider, that these principles of substantial forms, and accidents, and faculties, are not in reality any of the known properties of bodies, but are perfectly unintelligible and inexplicable.