"Oh, chaos! If we were inclined to talk about chaos, I should tell you that all was necessarily in motion, and that 'the breath of God moved upon the waters'; that the element of water was recognized in existence, and that the other elements existed also; that, consequently, fire existed; that there cannot be fire without motion, that motion is essential to fire. You will not succeed much with chaos." "Alas! who can succeed with all these subjects of dispute? But, as you are so very fully acquainted with these things, I must request you to inform me why one body impels another: whether it is because matter is impenetrable, or because two bodies cannot be together in one place; or because, in every case of every description, the weak is driven before the strong?" "Your last reason is rather more facetious than philosophical. No person has hitherto been able to discover the cause of the communication of motion." "That, however, does not prevent its being essential to matter. No one has ever been able to discover the cause of sensation in animals; yet this sensation is so essential to them, that, if you exclude the idea of it, you no longer have the idea of an animal." "Well, I will concede to you, for a moment, that motion is essential to matter--just for a moment, let it be remembered, for I am not much inclined to embroil myself with the theologians--and now, after this admission, tell me how one ball produces motion in another?" "You are very curious and inquisitive; you wish me to inform you of what no philosopher ever knew." "It appears rather curious, and even ludicrous, that we should know the laws of motion, and yet be profoundly ignorant of the principle of the communication of motion!" "It is the same with everything else; we know the laws of reasoning, but we know not what it is in us that reasons. The ducts through which our blood and other animal fluids pass are very well known to us, but we know not what forms that blood and those fluids. We are in life, but we know not in what the vital principle consists." "Inform me, however, at least, whether, if motion be essential to matter, there has not always existed the same quantity of motion in the world?" "That is an old chimera of Epicurus revived by Descartes. I do not, for my own part, see that this equality of motion in the world is more necessary than an equality of triangles. It is essential that a triangle should have three angles and three sides, but it is not essential that the number of triangles on this globe should be always equal." "But is there not always an equality of forces, as other philosophers express it?" "That is a similar chimera. We must, upon such a principle, suppose that there is always an equal number of men, and animals, and moving beings, which is absurd."