Aristotle’s longest and most comprehensive critical discussion of Empedocles’ natural philosophy occurs in GC II 6. He structures his criticism around four Empedoclean theses. (1) There are four kinds of elemental body and instances of these kinds do not change into one another. (2) Everything that comes to be by nature does so by chance. (3) Love and strife are the principles of natural bodily movement. (4) Soul is, or is constituted by, one or more of the four elemental bodies. I discuss Aristotle’s arguments against each of these theses in detail. Though Aristotle’s arguments are predominantly negative, we can view them as collectively constituting a sustained defense of the superiority of his preferred account. Aristotle’s natural philosophy centers on his novel understanding of nature as an internal principle and cause of movement and rest. I argue that the phenomena Empedocles is unable to explain adequately or endorse consistently are precisely the phenomena that Aristotle’s conception of nature is well-suited to explain.

In GC II 8, Aristotle shows that earth, water, air, and fire, are presented in every mixed body. Here Aristotle develops further the discussion of elemental mixtures started in GC II 7. He goes beyond anything done up to this point because the mixed bodies he is concerned with are not just the elemental mixtures discussed in GC II 7; rather, they are all the mixed bodies inhabiting the region around the center of the universe. Insofar as this region is the place where the natural processes of generation and corruption take place, GC II 8 prepares the grounds for the final section of the GC II (GC II 9-11).

In GC II 3, Aristotle gives an initial justification of three theses: (i) that there are four primary bodies; (ii) that these are earth, air, fire, and water; and (iii) that each is associated with two primary differentiae. Despite his laconic presentation, Aristotle offers an impressive variety of justifications for his main contentions: he appeals to combinatorial mathematics, to what is “in accordance with argument,” to empirical observation, and to his predecessors. I consider whether this chapter indicates that the primary bodies are not really elements; whether the “apparent simple bodies” Aristotle mentions are the primary bodies or something else; and how to understand the “fiery” and “airy” things that are not fire and air (respectively) but somehow like them. I find that the primary bodies are indeed genuine elements of sensible bodies for Aristotle; that the “apparent simple bodies” are the everyday counterparts of the elemental bodies; and that the contrast between fiery and airy things and fire and air is a contrast between the elemental bodies and their everyday counterparts.

In GC II 2, Aristotle discovers the contrarieties that constitute the principles of all perceptible bodies. They are the hot and the cold, the dry and the moist because they are the basic tangible contrarieties that interact as active and passive powers in a way that can result in a new affection. In GC II 2, Aristotle also attempts a reduction of all other tangible contrarieties to the basic four. I argue that the active/passive relation does not hold only between the two basic pairs of contrarieties but also within each pair. I compare the reduction of other contraries to the basic four with what Aristotle says in Meteor. IV. Despite minor differences and the wider scope of analysis in the latter work, Aristotle’s admirable effort to reduce the rich variety of tangible properties to a limited number of contraries and elements is the same.

GC II 7 supports Aristotle’s elemental theory, according to which the four elements possess a common matter that enables their inter-transformation, over the superficially similar Empedoclean one, by arguing that the former theory, and it alone, can accommodate the formation of homogenous stuffs like flesh and bone from the four elements. According to the interpretation offered here, these stuffs are mixtures in the sense spelled out in GC II 10, and appear to be exhibit the kind of strong uniformity that some interpreters have denied to Aristotelian mixtures. Special attention is devoted to bringing out the significance of elemental mixture for Aristotle’s twin projects in GC: understanding the causes of generation and destruction and establishing a theory of the elements. Explaining the formation of elemental mixtures is a crucial step in showing how the generation of more complex substances is possible and how the four elements, as he conceives them, function as elements of more complex substances.

GC II 9 resumes the task announced already in GC I 3: explicating generation and corruption so as to account for the fact that these processes are ontologically distinct from alteration. Aristotle identifies the causes of generation and corruption with a view to explaining their contribution in bringing these processes about. First, the chapter discusses the material cause and identifies the kind of matter that functions as a cause of these processes. Rather than presenting matter as merely passive the chapter paints a picture of it as contributing to the causation of generation by supplying the capacities without which form would be unable to fulfill its forming function, and as contributing to that of corruption by its readiness to both lose properties and gain others. The chapter goes on to censure Aristotle’s predecessors for failing to point to an efficient cause of generation and corruption, even though they claim that identifying such a cause is a principal motivation for their theorizing. Though largely critical, this discussion is carefully calibrated to unveil essential features of the efficient cause and in that way prepare the account for this cause in GC II 10.

This essay provides an analysis of GC I and explains why we now need to investigate the “so-called elements” – the primary bodies that make up all the more complex bodies of the sublunary world. This is an important passage for understanding how the discussion of the elements fits into the overall program of the whole work. In the second section, Aristotle broaches the question of whether there is a kind of matter “beyond” these elements. He criticizes two earlier theories which (he thinks) give an affirmative answer to this question: Anaximander’s theory of the apeiron and Plato’s theory of the Receptacle in the Timaeus. In the final section, Aristotle sets out his own position. This section is evidence that he was committed to prime matter – an ultimate material substratum which partially constitutes each of the primary sublunary bodies, and which underlies the process of elemental inter-transformation.

This essay provides basic exposition of GC II 11; for though the upshot of this difficult chapter is by and large clear, the argumentative details are often hard to make out. The question of the chapter is whether there is anything that comes to be of necessity; its answer, briefly put, is that there would be if there were anything whose coming to be was everlasting, which there would be if there were anything whose coming to be was cyclical, which in point of fact there is (e.g., solstices). The argument fails, of course; the reason, I suggest, is that it does not follow, from the fact that (say) solstices come to be cyclically, that they are always in process of coming to be.