Apeil 10, 1914] 



SCIENCE 



626 



and are quite independent of biology in any 

 respect whatsoever. Biology is neyertheless 

 dependent upon them, for life can manifest 

 itself only in active physico-chemical systems. 

 Thus a further and more interesting conclu- 

 sion arises: — In fundamental characteristics, 

 viz., in the physical and chemical properties of 

 water and carbonic acid and in various other 

 similar respects, the actual environment is the 

 fittest possible abode of life. 



To some of my critics this statement not 

 unnaturally seems extravagant.* But I hope 

 that this may be due to my failure clearly to 

 explain its meaning and its foundation, rather 

 than to a real fallacy in its development. Tor 

 in the first place it is to be observed that by 

 fundamental characteristics I mean just those 

 abstract physico-chemical properties like tem- 

 perature, concentration, stability, chemical ac- 

 tivity, etc., which can be measured. And in 

 the second place, I mean not merely a few of 

 such characteristics, but, so far as physical 

 science can recognize them, all such character- 

 istics. Now there can be no doubt that, in 

 respect to these things, water, carbonic acid 

 and the three elements are really unique, and 

 nobody who has examined the evidence has 

 thus far expressed a doubt of it. I need 

 hardly add that I am speaking of the world as 

 we know it and not of any hypothetical world 

 in which matter assumes unknown forms and 

 activities. 



The difiiculty, then, must lie in what ap- 

 pears to certain biologists, though I think 

 not to the physicists, as an unwarranted as- 

 sumption. This is that stability, wealth and 

 variety of supply of matter and energy, and 

 mobility thereof, and a host of other similar 

 characteristics, must be an advantage to life 

 in its effort to evolve, and that this is true not 

 merely of life as we know it, but of any possi- 

 ble life manifesting itself in the world as we 

 know it, in this world of our modern astron- 

 omy, physics and chemistry. Further, that the 

 greater the magnitude of these characteristics 

 the greater the advantage to life, and hence 



<R. S. Lillie, Science, N. S., XXXVIII., 337, 

 September 5, 1913; J. Arthur Thomson, Hibbert 

 Journal, p. 220, October, 1913. 



that, among the compounds and elements 

 which we know, the environment made of 

 water and carbonic acid on a planet's surface 

 is the fittest. Of course I do not mean this 

 planet — this earth — but any planet constituted 

 like those of our universe; for I am dealing 

 abstractly, not specifically, with cosmic evo- 

 lution. 



This difficulty raises the question, which 

 evidently can be but imperfectly answered, 

 what are, speaking generally and abstractly, 

 the relations between any material system and 

 the rest of the world? This, once more, is a 

 purely physico-chemical problem. 



As a result of the thermodynamical studies 

 of Willard Gibbs and his development of the 

 phase rule, a large part of modern physical 

 chemistry is concerned with the classification 

 of systems, their activities, and the conditions 

 of equilibrium within them. An aggregate of 

 matter occupying a position of space is a 

 physico-chemical system. In physical chem- 

 istry it is customary, for the sake of the sim- 

 plification, to study closed systems, that is to 

 say, systems which are not exchanging matter 

 or energy with the outside world. But it is 

 quite possible to proceed from these closed sys- 

 tems to such as are exchanging matter and 

 energy with their environment. Now the 

 phase rule has made possible a very complete 

 and exhaustive classification and description 

 of systems in a perfectly abstract way." 

 Necessarily, therefore, it has provided a com- 

 plete qualitative physical and chemical analy- 

 sis of the fundamental characteristics of any 

 system. 



In addition to its material and spatial char- 

 acteristics a system must manifest activity. 

 In the very simplest case it will at least exhibit 

 that motion which we call heat. But activity 

 also has been brought completely under the 

 sway of physical science, for energetics deals 

 exhaustively with all forms of physical and 

 chemical activity. 



5 It must be pointed out that there is a certain 

 incompleteness, which happily is of minor impor- 

 tance for our present purpose, in the failure to 

 take account of such a thing as electrical poten- 

 tial. 



