Experience, I say, every moment furnishes us with the clear ideas both of the one and the other.

But beyond these ideas, as received from their proper sources, our faculties will not reach.

If we would inquire further into their nature, causes, and manner, we perceive not the nature of extension clearer than we do of thinking.

If we would explain them any further, one is as easy as the other; and there is no more difficulty to conceive how A SUBSTANCE WE KNOW NOT should, by thought, set body into motion, than how A SUBSTANCE WE KNOW NOT should, by impulse, set body into motion.

So that we are no more able to discover wherein the ideas belonging to body consist, than those belonging to spirit.