to conceive as if motion were a substantial thing and resembled salt dissolved in water, which comparison is actually the one M. Rohaut,' if I mistake not, has used. I add here that this is not even the most usual case, for I have elsewhere demonstrated that the same quantity of motion is maintained only when the two bodies which come into collision proceed in one and the same direction before the collision and still proceed in one and the same direction after the collision. It is true that the veritable laws of motion are derived from a cause superior to matter. As for the power of producing motion by thought, I do not think we have any idea of it, as we have no experience of it. The Cartesians themselves admit that souls cannot give a new force to matter, but they pretend that they give it a new determination or direction of the force it has already. For myself, I maintain that souls change nothing in the force nor in the direction of bodies; that the one would be as inconceivable and unreasonable as the other, and that you must avail yourself of the pre-established harmony in order to explain the union of the soul and the body.] Ph. It is worth our consideration whether active power is not the proper attribute of spirits and passive power of bodies? Whence we might conjecture that created spirits, being active and passive, are not totally separate from simply passive matter; and that these other beings, which are active and passive at the same time, partake of both. Th. [These thoughts greatly please me and entirely express my conviction, provided you explain the word spirit so generally that it comprises all souls, or rather (to speak still more generally) all the entelechies or substantial unities, which are analogous to spirits.] . Ph. I much wish that you would show me in the notion we have of spirit anything more confused] or nearer a contradiction than what the very notion of body includes. I mean infinite divisibility. Th. [What you here say further in order to make evident that we understand the nature of the spirit as well or better than that of the body is very true; and Fromondus, who has published a book, De compositione continui, was right in entitling it Labyrinth. But the question arises from a false idea you have of the nature of body as well as of space.] . Ph. The idea of God indeed comes to us as others do, the complex idea of God we have being composed of the simple ideas which we receive from reflection and which we extend by the idea