Zeno (c. 465 BCE) was a student of Parmenides and evidently a great admirer of his teacher’s famous claim, "There is a way which is and a way which is not" so much so that he set about to write a series of paradoxes to prove it empirically.
From Aristotle, primarily, it is known that once there were 40 paradoxes penned by Zeno of which there exist less than ten today. The most famous of these paradoxes are The Race Course, The Achilles and The Arrow.
The Race Course argues that, in order for someone to move from Point A to Point Z one must first get to the halfway point between A and Z. However, in order to reach that halfway point one must get to the halfway point between Point A and that halfway point and, to reach that spot, one must travel halfway again. Since there will always be a space, even an infinitesimal one, between one point and another, and since one must always move halfway before one may reach one's destination, motion is impossible. Our senses, which tell us that motion is possible, must then be flawed and should not be trusted to apprehend truth.
The Achilles argument claims that the swiftest runner will never overtake the slowest who starts the race first, "inasmuch as, reckoning from any given instant, the pursuer, before he can catch the pursued, must reach the point from which the pursued started at that instant, and so the slower will always be some distance in advance of the swifter" (Baird/Kaufmann, 28). In other words, because the slower runner (usually depicted as a tortoise while the swifter is known as 'Achilles') is in advance of the swifter, the swifter must first arrive at that point where the slower runner began and, as the slower will always be ahead of the swifter by virtue of having started earlier, the swifter must always be in pursuit of the slower without ever having hope of catching him.
The Arrow, another argument against the reality of motion, shows how an arrow in flight cannot possibly move as "everything is at rest when it is in a place equal to itself, and if the moving object is always in the present [and therefore in a place equal to itself] then the moving arrow is motionless" (Robinson, 134). Since all we live in, at any moment, is the present and since the arrow is motionless at any given moment in its flight, the arrow cannot actually be moving.
The intended aim of Zeno's paradoxes was to prove the vision of Parmenides, that there was a way of truth (logic) and a way of opinion (the senses) and how, clearly, the senses could not be trusted to lead one to an apprehension of Truth with a capital T. Far from being simple word-puzzles, however, the paradoxes gave rise to a method of analysis and discussion of a question, known as dialectic, which proved a most valuable tool in philosophical inquiry. "Dialectic involves two people: a questioner and an answerer. The questioner invites the answerer to take up a position which he thinks he can defend, and proceeds by a series of well-placed questions to drive him from it. He does this by getting the answerer to agree to a series of further propositions which, taken together, imply the contradictory of the original thesis"(Robinson, 137). It is obvious the effect this had on the young writer, Plato. Plato's Dialogues are virtual handbooks on the art of dialectic. In Republic dialectic is used to find out what justice is, in Euthyphro, Piety, in Ion it is 'What is Art' and in Meno, what constitutes Virtue is sought through the dialectic method. Whether he intended to, Zeno gave to ancient Greece the art of dialectic and handed to Plato the means by which the latter would then lay the groundwork for western philosophy.
(Portions of this piece previously published on Suite 101 by Joshua J. Mark).