 Limit and the Unlimited are also principles active among mathematical entities (On General Mathematical Science, chap. 13). Here they play a role similar to that of the pairs Monad and Dyad, Odd and Even, or Same and Other according to Nicomachus of Gerasa, the neo-Pythagorean author of the Introduction to Arithmetic and one of Iamblichus’ intellectual heroes; similar pairs studied by the mathematical sciences are “continuous” and “discrete” (sunekhes, diōrismenon), “magnitude” and “plurality” (megethos, plēthos: cf. Nicomachus, Intr. arith. I, 2, 4–5), all of which concur to form a dynamic picture of reality. The four mathematical sciences—arithmetic, which takes precedence over the others; geometry, music and astronomy—each study a corresponding kind of being, and were the object of On Pythagoreanism vol. IV and VIII–X respectively (see the plan of the work as outlined by O’Meara 1989).