462 SCIENTIFIC THOUGHT. 



methods of investigation and reasoning which have 

 been learnt in the mechanical, physical, and chemical 

 sciences : the processes of observation, measurement, 

 and calculation. And yet it may be asked, have we 

 come nearer an answer to the qviestion, What is Life ? 

 At one time, for a generation which is passing away, 

 we apparently had. But a closer scrutiny has convinced 

 most of us that we have not. The study of life has 

 indeed been transferred from the higher and more com- 

 plex forms to the lower, the minuter, and the simpler ; 

 and now lingers by preference among cells, germs, and 

 primitive organisms, out of which we have learnt to 

 consider the higher ones as put together on the prin- 

 ciples of co-operation, division of labour, and mutual 

 57. accommodation. The problem " What is Life ? " has 



Two aspects 



of the in all this sained a twofold aspect. Wherein consists 



problem ^ ^ 



of life. ^Yie peculiarity of the smallest unit of living as com- 

 pared with not-living matter ? In organisation we are 

 told, in growth through intussusception, in metabolism ; 

 but we are far from being able mechanically to describe 

 these phenomena or processes. The spectre of a vital 

 principle still lurks behind all our terms.^ On the other 



^ If we broadly summarise the 

 properties peculiar to living things 

 which the nineteenth century has 

 dwelt on in an original manner 

 under the three conceptions of adap- 

 tation (fitness), selection (natural or 

 sexual), and organisation (order or 

 harmony), the question presents it- 

 self. Is any of these much-used terms 

 intelligible or definable without 

 reference to something which is ex- 

 traneous to the object we treat of, 

 this reference existing in our own 

 thinking or contemplating mind, 

 and, if actually present in natural 



objects themselves, then also indi- 

 cative of the existence of some im- 

 material principle ? Though this is 

 manifested in mechanical contriv- 

 ances which it has left behind with 

 its signature upon them, it is never- 

 theless vaguely analogous to the 

 selective, purposeful, or orderly 

 jjerformances of a human intellect 

 The exclusive study of detail on the 

 one side, the aspect of the whole on 

 the other, will always induce opposite 

 answers to this question. In addi- 

 tion to the literature given in the 

 notes to this chapter, I may refer 



