Seite - 108 - in The Priority of Locomotion in Aristotle’s Physics

4.4.4 Every change in the four basic qualities involves condensation or rarefaction So far it has become clear that Aristotle in saying that πύκνωισς and μάνωσις are principles of all qualities and hence of all alteration, is claim- ing that any such changes involve some change in density that occurs with respect to the thing that alters. I have already presented the first part of the reason for this claim, namely that any change in quality necessarily involves a concomitant change with respect to the four basic qualities of the change’s subject. Now I will argue that this change of the four basic qualities necessa- rily involves condensation and rarefaction, and in consequence, it will become clear that every alteration, in virtue of occurring by means of a change in the four elemental qualities, always goes hand in hand with con- densation or rarefaction. That a change from hot to cold, or vice versa, goes hand in hand with condensation and rarefaction is clear from examples stated at an earlier point in the discussion. As each of the elemental bodies becomes hotter or colder, a change in volume also occurs. As we have seen, as water is heated it expands and becomes more rarefied, but contracts when cooled. The same is true of the other elements. This already suffices, since these phe- nomena according to Aristotle can be explained by making use of the con- cepts of condensation and rarefaction. But, as we have seen, for the argument to work, condensation and rare- faction also have to be “sources” of dry and moist, as well as of the change from one of the two contraries to the other. Although Aristotle does not explain in what sense this is the case, I think it follows from his theory inso- far as it can be inferred from the role the basic qualities of dry and moist play for the simple bodies. To which of the four elements an elemental body belongs, i.e. which form it has, depends on the way in which the four basic kinds of qualities are combined. Fire is characterised by the qualities of hot and dry, air by hot and moist, water by cold and moist, and earth by cold and moist.101 If an element is affected in such a way that one of its defining qualities turns into its contrary, then the elemental body as this particular elemental body perishes, and a new one that belongs to the kind of simple bodies characterised by the new combination of the basic qualities comes to be. If, for example, water, which is essentially characterized by a combina- tion of cold and moist, is affected in such a way that its being moist is over- come (κρατεῖν) by dryness, as Aristotle puts it, then the water perishes in the process, and earth, which is cold and dry, comes to be instead.102 Con- 101 See GC II 3, 330b1–9. 102 See GC II 4, 331a32–36. 108 Locomotion necessarily accompanies each of the other kinds of change ISBN Print: 9783525253069 — ISBN E-Book: 9783647253060 © 2014, Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen