vi. 9; 239 b 5. And Zeno’s reasoning is fallacious. For if, he says, everything is at rest [or in motion] when it is in a space equal to itself, and the moving body is always in the present moment <in a space equal to itself,> then the moving arrow is still. This is false; for time is not composed of present moments that are indivisible, nor indeed is any other quantity. Zeno presents four arguments concerning motion which involve puzzles to be solved, and the first of these shows that motion does not exist because the moving body must go half the distance before it goes the whole distance; of this we have spoken before (_Phys._ viii. 8; 263 a 5). And the second is called the Achilles argument; it is this:—The slow runner will never be overtaken by the swiftest, for it is necessary that the pursuer should first reach the point from which the pursued started, so that necessarily the slower is always somewhat in advance. This argument is the same as the preceding, the only difference being that the distance is not divided each time into halves.... His opinion is false that the one in advance is not overtaken; he is not indeed overtaken while he is in advance; but nevertheless he is overtaken, if you will grant that he passes through the limited space. These are the first two arguments, and the third is the one that has been alluded to, that the arrow in its flight is stationary. This depends on the assumption that time is composed of present moments; there will be no syllogism if this is not granted. And the fourth argument is with reference to equal bodies moving in opposite directions past equal bodies in the stadium with equal speed, some from the end of the stadium, others from the middle; in which case he thinks half the time equal to twice the time. The fallacy lies in the fact that while he postulates that bodies of equal size move forward with equal speed for an equal time, he compares the one with something in motion, the other with something at rest. (_c_) PASSAGES RELATING TO ZENO IN THE DOXOGRAPHISTS. Plut. _Strom._ 6; _Dox._ 581. Zeno the Eleatic brought out nothing peculiar to himself, but he started farther difficulties about these things. Epiph. _adv. Haer._ iii. 11; _Dox._ 590. Zeno the Eleatic, a dialectician equal to the other Zeno, says that the earth does not move, and that no space is void of content. He speaks as follows:—That which is moved is moved in the place in which it is, or in the place in which it is not; it is neither moved in the place in which it is, nor in the place in which it is not; accordingly it is not moved at all. Galen, _Hist. Phil._ 3; _Dox._ 601. Zeno the Eleatic is said to have introduced the dialectic philosophy. 7; _Dox._ 604. He was a skeptic.