300 DRIESCH'S THEORIES OF DEVELOPMENT V 



most general expression for the facts with which it deals, but 

 the ultimate conceptions of each, as in Aristotle's series of ' souls } , 

 are necessarily involved in the one next above, while conversely 

 each endeavours to translate its own ultimates into those of the 

 science below : a translation, however, which, be it never 

 forgotten, leaves the reality of the original undestroyed. 



Thus, mechanics expresses molar motions in terms of pure 

 numbers, physics explains forms of energy heat and light and 

 electricity as the motions of molecules ; chemical affinity is to 

 be reduced to the mutual attractions of intramolecular atoms ; pur- 

 posive responses to stimuli may be stated in terms of chemical 

 reaction, and the psychical phenomena of mental and moral 

 science understanding and feeling and will are a form of these. 



The cosmic process thus takes place in a succession of stages, 

 and the peculiar features which mark each individual stage 

 are simply the outcome of an increase in complexity of the 

 peculiarities characteristic of the stage below. To establish this 

 is the final achievement of science. 



Nevertheless, the facts with which each science starts, the 

 facts which come first in the order in which knowledge is 

 acquired, do not become wholly merged in those simpler facts 

 into which they are at each stage translated ; when the translation 

 has been accomplished the original still remains. 



The ' secondary qualities ', as well as the other properties of 

 those bodies whose behaviour the physicist investigates, are 

 as real as, no more and no less relative to our intelligence than, 

 those ' primary qualities ' of impenetrability and extension 

 exhibited by those bodies whose behaviour forms the subject- 

 matter of mechanical science into which it is his endeavour to 

 translate them, just as the primary qualities themselves obstin- 

 ately refuse to be reduced to mere number. Chemical affinity 

 remains as a phenomenon sui generis after it has been reduced to 

 the operations of intramolecular forces, and the purposiveness 

 of responses to stimuli is something over and above the chemical 

 reactions to which they are rightly referred. Last of all, the 

 final term in the series, the mental and moral consciousness, 

 the 'other side' of certain purely physical functionings of the 

 organism, is as real as any of those qualities of matter which 



