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3 



automatically by a machine constructed for that purpose. This 

 might be the case if all we knew was that the removal of the 

 wood caused the house to be built without floors or roof but if 

 we observed that after all the materials were mixed together 

 indiscriminately and then half carted away, a house half the 

 normal size appeared, we should infer that a directing intelli- 

 gence was present which did the best that was possible with 

 the available materials. The only " machine " conceivable in 

 this latter case would be one consisting in the mutual attractions 

 or affinities of the constituent parts (cf. the comparison to a 

 magnet given above) but to account for the development and 

 differentiation of an organism by such hypothesis is to bring 

 into play a whole array of physico-chemical forces which at 

 present are quite unknown and is in fact vitalism ashamed to 

 call itself by its proper name. The fallacy of this kind of 

 criticism of Driesch's hypothesis lies in the assumption that 

 because certain substances are necessary for the development of 

 certain parts, they are the " cause " of that development ; beams 

 or girders may be necessary for the production of the floors 

 in a building but they cannot be called their cause ; if the 

 beams provided for the purpose were removed while the build- 

 ing was in progress and it was then found that arches of brick 

 were substituted, at least a. prima facie case would be made out 

 for a directing intelligence rather than a machine. It is to facts 

 of this order that Driesch appeals in support of his hypothesis 

 and although he perhaps goes too far in saying that the possi- 

 bility of a machine is excluded, his contention cannot be opposed 

 by proving that certain materials are necessary for certain 

 results, unless it can be shown that those materials are sufficient 

 in themselves to bring the results about. The chemistry and 

 ptrysics of living matter may be able to do this in the future 

 but are far from doing so at present ; therefore for the present 

 his position is unassailable in this direction. 



The matter can only be furthered by careful observation and 

 well-planned experiment, in which the biologist must work in 

 co-operation with the physicist and chemist. At the present 

 time the student of living things shows a tendency to regard 

 any phenomenon as "explained" when once it falls under 

 known laws of physiological stimulation or metabolism, although 

 the ultimate causes of these things are unknown. It rests 

 with the future to discover whether they have a purely 



