A Milesian philosopher claimed that opposites like hot and cold are derived from this concept, then return to it by destroying each other. This word is the typical translation of apeiron, which was Anaximander’s first principle. The modern theory of supertasks, which have this property, resolves an ancient paradox (-5[1])that was formulated to justify Parmenides’ monism. Aristotle invoked a “first cause” to avoid a “regress” named for this concept. Zeno of Elea argued that an arrow must travel half the distance to its target this many times, so motion is impossible. For 10 points, name this mathematical concept that refers to something bigger than any natural number. ■END■ (10[1])