CONTINUITY OF VITAL PROCESSES 41 



reached the Theoretical stage. This stage has three 

 subdivisions : the purely hypothetical, when the con- 

 nections are perceived as mere conjectures, the ex- 

 perimental, when the conjectures guide experiments, 

 and the mathematical, where the phenomena are 

 merely the results of certain laws by which they 

 can be predicted when particular conditions are 

 known. 



Biology, although it has reached the Theoretical 

 stage, is merely in the hypothetical subdivision of 

 this stage. No general law has yet been found to 

 prevail throughout the science of life. The survival of 

 the fittest or natural selection is largely a truism, and 

 another way of saying that Nature does what it does 

 and cannot help doing. It, however, like many 

 truisms, emphasises the fact that there is a continual 

 struggle between an individual and its surroundings, 

 and that only those that can withstand that struggle 

 are the ones which can survive. There is selection 

 because the unfit are eliminated. 



It accounts for the presence of things we should 

 otherwise see no reason for ; but it is not a theory in 

 the strictest sense. We can explain phenomena, but 

 we cannot predict them. It does not enable us to 

 penetrate into the principle which underlies the 

 struggle for existence between the individual and its 

 environment. What it is that enables the individual 

 to persist in certain circumstances and prevents it 

 from doing so in others. As soon as we can frame 

 theories which suggest experiments and obtain 

 experimental results which enable us to frame 



