ORGANISM AND MECHANISM 109 



does not recognise mental factors as verce causce at all, and 

 as there are organisms and vital activities which are not 

 known to have any mental aspect, we shall leave this limit 

 to mechanistic description for future consideration. 



So the first question is whether, mentality apart, there are 

 irreducible peculiarities in vital activities peculiarities 

 which cannot be adequately accounted for in terms of 

 physico-chemical or ideally mechanical description? Or is 

 the usually admitted incompleteness of the physico-chem- 

 ical description of, let us say, a reflex action merely tem- 

 porary, and likely soon to disappear ? 



The second question is a little different. Of the move- 

 ments of the heavenly bodies Gravitational Astronomy gives 

 mechanical descriptions which are practically exhaustive 

 and almost perfectly useful. Now, supposing there were 

 available a complete mechanical account of, say, the open- 

 ing of a Yucca flower, would that be all that is wanted in 

 Biology? Would light have been thrown, for instance, on 

 the fact that only one Yucca flower opens on each plant 

 each evening, that the flowers begin to open when the Yucca 

 moths begin to emerge from their cocoons, that the life of 

 the flower and the life of the moth are closely bound up 

 together, so that the one without the other is not made 

 perfect? The Yucca flower and the Yucca moth are or- 

 ganisms with a history; they have come to work into one 

 another's hands. Are their adaptive relations only different 

 in degree from the dynamical relations between Earth and 

 Moon, or must we admit that the answers to distinctively 

 biological questions do not follow from even a complete 

 ledger (were that available) of the chemical and physical 

 transactions ? 



