AND ITS SELF-CONSERVATION. 117 



And that this is by no means a strained interpretation 

 is shown in a remarkable passage of the "Metaphysics," 

 (Lib. XL [XII. ] cap. II). The entire book is devoted to 

 a discussion of substance. In the second chapter change 

 is especially considered as pertaining to that phase of sub- 

 stance perceptible to the senses. In the preceding chap- 

 ter he has remarked that in this phase of substance there 

 is an eternal element or factor. Here he indicates that 

 this permanent factor in the midst of the changing is to 

 be called matter (obj). Directly after is found the pas- 

 sage to which reference is made above, and which is as 

 follows: "If there were four modes of change one as 

 to type (TO ri), one as to quality (TO notov), one as to 

 quantity (ij noffov), one as to place (ij TTD); and if sim- 

 ple integration (yfrsffis) and 1 disintegration (QOopa) [were 

 to take place] according to the first of these modes, in- 

 crease and diminution according to that of quantity, 

 change, [in quality] according to passivity, and motion 

 according to place; then in every case change would be 

 a contradiction." Thus far, as if with reference to the 

 Zenonian arguments in disproof of the possibility of 

 change. But he adds immediately a statement that 

 seems to refer distinctly to the Heraclitean doctrine of 

 Becoming as the essentially true one in respect of change. 

 The statement is this: "Whence, of necessity, all possi- 

 ble change in matter is two-fold [or of reciprocal nature] . 

 But, since being is two-fold, everything changes from 

 potential being (duvdpst OVTOS) into real being (ivsp^sia 6v); 

 as, for example, from light potential to light real. Simi- 

 larly with increase and diminution. Whence it is by no 

 means accidental that all things are developed recipro- 



