1. Anaxagoras did not believe that there is something which is indivisible into parts, did believe that there more than one existing thing, did believe that at a fundamental level nothing comes to be or perishes, and did not believe that, loosely speaking, many things come to be and perish. The Atomists believed that there is something which is indivisible, did believe that there is nevertheless more than one existing thing, did not believe that nothing comes to be or perishes, and did believe that many things comes to be or perish. Despite many contradictions and vagueries which at times bring both Anaxagoras and the Atomists to the verge of mysticism and/or nonsense, these general beliefs, some with undeniable qualifications, are fair conclusions to draw from their statements and from McKirahan's analysis.
Anaxagoras believed that "there is coming to be or perishing. . . . What appear to be cases of coming to be and perishing are really instances of mixture and separation of existing things. . . . Coming to be is simply mixture and perishing is simply separation" (203; 204).
Democritus and Leucippus, the Atomists, on the other hand, "make alteration and coming to be out of [the changing shapes of existing things]: coming to be and destruction by means of separation and combination, alteration by means of arrangement and position" (305). Therefore, for the Atomists, many things---indeed, everything, since everything changes shape---come to be and perish.
Anaxagoras did not believe that there is something which is indivisible into things: "There are many . . . different types of basic things." He "posit[s] a vast number of different kinds of things" and argues that "things are not composed of ultimate indivisible pure particles" (203; 216). A qualification on this belief can be discerned in Anaxagoras' "commit[ment] to nonseparable, noncountable amounts of the Basic Things, the Portions" (205). Clearly, then, for Anaxagor...