230 THE MECHANISM OF LIFE 



in space and time. It would be highly inconvenient in the 

 practical affairs of life to do otherwise, and it would be clumsy 

 even in scientific investigations. Just now, however, we are not 

 concerned with practice, but with the attempt to search into the 

 meaning of things. 



These meanings we can grasp in a fumbling kind of way. We 

 postulate relata between which we make differential equations or 

 relations. But the relata are only space-time coincidences, 

 ds's and dt's, and these have no " reality " apart from co-ordinate 

 frames to which we refer them, and the choice of such co-ordinate 

 frames is quite arbitrary. Something, however, is an absolute 

 element of our knowledge, and this is the relation itself which 

 exists, and is invariant even if the frames of reference vary. 



Obviously, then, " our knowledge of nature is a knowledge of 

 form and not of content,"* and what that content is we do not 

 know. We are assuming (though the assumption cannot be 

 proved " scientifically ") that there is a content of nature some- 

 thing apart and independent of the intuition of life. The latter 

 works itself out in a description of the manner in which it acts upon 

 the content, but it does not describe the content. That is the 

 ordinary, " natural " way in which we think about things here 

 is life, in us as well as in a multitude of other animals, and there 

 is an " environment " upon which life acts. That assumption 

 is contained in everything that an animal does, and it is implicit 

 in all our civilisations, and so one cannot but make it a part of 

 our philosophy. We know imperfectly how we act upon nature 

 (the environment), but we do not know what it is that we act 

 upon. The elements of our scientific knowledge are the forms 

 of the actions, but not the stuff acted upon. 



The " Passage of Nature."t Assuming, then, this nature that 

 exists independently of our form and power of action upon it, 

 we note that it " passes " that it is a progress or career. It has 

 a tendency in a particular direction, that tendency being described 

 by the second law of energetics. This law we must regard as the 

 fundamental thing in our experience, the concept that is un- 

 shaken by any recent development of scientific theory and specu- 

 lation. And, of course, its fundamental character suggests that 

 the law is in us in our mode of acting upon nature. 



First, we note the phenomena of radio-activity. Certain ex- 

 ceptional substances the atoms of uranium, radium, actinium, 



* Eddington, Space, Time and Gravitation, Cambridge University Press, 

 1920, p. 200. 



t A. S. Whitehead, The Concept of Nature, Clarendon Press, 1920. 



