However, let us go a step further, and, out of excessive complaisance, suppose that all the bodies in Nature are actually in motion. Does it follow from thence that motion is essential to every particle of matter? Besides, if all bodies have not an equal degree of motion; if some move sensibly, and more swiftly than others; if the same body may move sometimes quicker and sometimes slower; if a body that moves communicates its motion to the neighbouring body that was at rest, or in such inferior motion that it was insensible--it must be confessed that a mode or modification which sometimes increases, and at other times decreases, in bodies is not essential to them. What is essential to a being is ever the same in it. Neither the motion that varies in bodies, and which, after having increased, slackens and decreases to such a degree as to appear absolutely extinct and annihilated; nor the motion that is lost, that is communicated, that passes from one body to another as a foreign thing--can belong to the essence of bodies. And, therefore, I may conclude that bodies are perfect in their essence without ascribing to them any motion. If they have no motion in their essence, they have it only by accident; and if they have it only by accident, we must trace up that accident to its true cause. Bodies must either bestow motion on themselves, or receive it from some other being. It is evident they do not bestow it on themselves, for no being can give what it has not in itself. And we are sensible that a body at rest ever remains motionless, unless some neighbouring body happens to shake it. It is certain, therefore, that no body moves by itself, and is only moved by some other body that communicates its motion to it. But how comes it to pass that a body can move another? What is the reason that a ball which a man causes to roll on a smooth table (billiards, for the purpose) cannot touch another without moving it? Why was it not possible that motion should not ever communicate itself from one body to another? In such a case a ball in motion would stop near another at their meeting, and yet never shake it. SECT. LXXX. The Rules of Motion, which the Epicureans suppose do not render it essential to Bodies.