346 THE GRAMMAR OF SCIENCE 



everyday routine.-^ We have seen (p. 330) that the 

 latter fact has been used by "VVeismann as an argument 

 in favour of the spontaneous generation of Hfe — " that 

 which can be completely resolved into inorganic matter 

 must also have arisen from it and must owe its ultimate 

 foundation to it," he writes. This passage seems to be 

 rather too dogmatic and to suggest a metaphysical sub- 

 stratum to sense-impression which is " completely resolved." 

 The argument would only be a valid one if we could 

 assert that all sequences of sense-ijupressions are reversible^" 

 but this is too wide a statement to be laid down un- 

 restrictedly in the present state of scientific knowledge. 

 Physicists will recall processes like the degradation of 

 energy, of which they are unable to at present conceive 

 any reversion. It may be that their perceptual experience 

 is not wide enough, and that their geometrical and 

 mechanical laws are only applicable to a certain portion 

 of the universe, or it may be, after all, that sequences are 

 irreversible. Hence the spontaneous generation of life does 

 not follow as a " logical necessity " from the transition of 

 living into lifeless substance, at least as long as we cannot 

 reasonably infer the reversibility of all sequences of sense- 

 impressions. 



S 7. — The Origin of Life 



Those who accept the evolution of all forms of life 

 from some simple unit, a protoplasmic drop or grain — 

 and this scientific formula is so powerful as a means of 

 classification and description that no rational mind is 

 likely to discard it — will hardly feel satisfied to stop at 

 this stage. They will demand some still more wide- 

 embracing formula, which will bring under one statement 

 their perceptual experience of both the living and the 

 lifeless. Here the physicist comes in with some very 

 definite conclusions. He tells us that in order to classify 



1 For example, in the boiling of impure water or in the pouring of acid on 

 vegetable matter, but hardly in the ordinary "death" of a complex animal 

 organism. 



2 See Appendix, Note VII. 



