Wherefore, in order to determine, wherein the human mind differs from other things, and wherein it surpasses them, it is necessary for us to know the nature of its object, that is, of the human body. What this nature is, I am not able here to explain, nor is it necessary for the proof of what I advance, that I should do so. We may thus recognize the superiority of one mind over others, and may further see the cause, why we have only a very confused knowledge of our body, and also many kindred questions, which I will, in the following propositions, deduce from what has been advanced. Wherefore I have thought it worth while to explain and prove more strictly my present statements. In order to do so, I must premise a few propositions concerning the nature of bodies.
All bodies are either in motion or at rest.
Every body is moved sometimes more slowly, sometimes more quickly. Bodies are distinguished from one another in respect of motion and rest, quickness and slowness, and not in respect of substance . The first part of this proposition is, I take it, self-evident. It is brought out still more clearly from E1P15N . All bodies agree in certain respects.