Mechanism, Vitalism, and Teleology 



plained. For example, the mechanism of trial and error by 

 which Paramecium avoids extremes of heat and cold is 

 based upon its ability to distinguish between favorable and 

 unfavorable, or between satisfactory and unsatisfactory, 

 conditions. In some of the simplest forms of living things 

 as well as in the most complex this capacity exists, and for 

 the present at least it cannot be accounted for on mechanis- 

 tic grounds. Thus in our mechanistic explanation of fitness 

 we put in at the beginning what we get out at the end, 

 namely, a capacity to distinguish between the fit and the 

 unfit, and a tendency to retain the one and eliminate the 

 other. And so in all mechanistic sciences from mathematics 

 to biology, we introduce in one form or another in our 

 factors the qualities which we seek to explain in the end 

 product. It is said that in some rural districts hogs are 

 weighed by driving them on to one side of a balanced plat- 

 form, throwing stones on to the other side until they equal 

 the weight of the hogs, and then guessing at the weight of 

 the stones. When we attempt to explain the actual origin of 

 fundamental qualities by quantitative mechanistic methods, 

 do we not, with much labor, perform a similar operation? 

 It is a striking fact that at present it is impossible to explain 

 the organization of a cell, the potencies of development or 

 of evolution, or the elements of fitness, purpose, and con- 

 sciousness on purely mechanistic grounds. "It is because liv- 

 ing things are irritable, registrative, persistent, variable, that 

 they have been able to evolve in adaptive ways," but we can- 

 not explain the fact that they possess these qualities. Thus 

 we introduce on one side of the equation the equivalents of 

 the things on the other side which we seek to explain. 



In a recent treatise on evolution in its widest aspects, 

 Macfarlane 1 has proposed as one of the principal factors in 



"'Causes and Courses of Organic Evolution," p. 628. , 



