This is also apparent in mechanics; of two bodies the question as to which moves presents itself before us. It requires more than two places—three at least—to determine which of them moves. But it is correct to say this, that motion is plainly relative; whether in absolute space the eye, for instance, rests, or whether it moves, is all the same. Or, according to a proposition brought forward by Newton, if two bodies move round one another in a circle, it may be asked whether the one rests or both move. Newton tries to decide this by means of an external circumstance, the strain on the string. When I walk on a ship in a direction opposed to the motion of the ship, this is in relation to the ship, motion, and in relation to all else, rest. In both the first proofs, continuity in progression has the predominance; there is no absolute limit, but an overstepping of all limits. Here the opposite is established; absolute limitation, the interruption of continuity, without however passing into something else; while discretion is presupposed, continuity is maintained. Aristotle says of this proof: “It arises from the fact that it is taken for granted that time consists of the Now; for if this is not conceded, the conclusions will not follow.” (d) “The fourth proof,” Aristotle continues, “is derived from similar bodies which move in opposite directions in the space beside a similar body, and with equal velocity, one from one end of the space, the other from the middle. It necessarily results from this that half the time is equal to the double of it. The fallacy rests in this, that Zeno supposes that what is beside the moving body, and what is beside the body at rest, move through an equal distance in equal time with equal velocity, which, however, is untrue.” 1 _E_|——|——|——|——|_F_ _k_ _i_ _m_ _C_|——|——|——|——|_D_ _g_ _n_ _h_ _A_|——|——|——|——|_B_ In a definite space such as a table (A B) let us suppose two bodies of equal length with it and with one another, one of which (C D) lies with one end (C) on the middle (g) of the table, and the other (E F), being in the same direction, has the point (E) only touching the end of the table (h); and supposing they move in opposite directions, and the former (C D) reaches in an hour the end (h) of the table; we have the result ensuing that the one (E F) passes in the half of the time through the same space (i k) which the other does in the double (g h); hence the half is equal to the double. That is to say, this second passes (let us say, in the point l) by the whole of the first C D. In the first half-hour l goes from m to i, while k only goes from g to n. 1 _E_|——|——|——|——|_F_ _k_ _o_ _i_ _m_ _C_|——|——|——|——|_D_ _g_ _n_ _h_ _A_|——|——|——|——|_B_