Thoughts on Causality. 



241 



with increase of cold, and as a sequence of it, the imme- 

 diate cause is evidently the increased amount of assimila- 

 tion at the growing points of the hairs. That cold is the 

 cause of this, there is no ground for asserting. But if it 

 were the cause, cold itself is the effect of a remoter cause — 

 the diminution of heat-vibrations ; and this is the result of 

 a decrease of energy in the cause of heat-vibrations — what- 

 ever that may be. When the common potato is grown 

 in a dry and sterile soil, it deteriorates in size and quality; 

 and the Darwinist would assert that these changes are 

 caused by the change in the environment; while in fact, 

 they are only conditioned by it. The change in the soil is 

 the condition of the assimilation of less material ; it is the 

 condition of the less energetic action of the vital forces. 

 Whatever result ensues, it is these forces which cause it. 

 The crane's long legs and the duck's broad bill are coordi- 

 nated to their environment, and have been fashioned as 

 they are by some cause. It is evident that the environment 

 has been the condition with reference to which the conform- 

 ation was produced. But there is no particle of proof 

 that the environment produced them. It would be inter- 

 esting to contemplate Professor Tyndall in the effort to 

 represent to his mind's eye the process by which pond-water 

 wove the web of a duck's foot ; or that by which the con- 

 sumption of clover-heads fashioned a persistent pulp in 

 the molar of the rabbit, while forest fruits determined a 

 limited growth in the molar of its fellow rodent, the squir- 

 rel. The whole doctrine of organic transformations, or 

 formations, through the influence of external conditions, 

 is infected with this fallacy of reasoning. I am not deny- 

 ing the coordinations alleged, but I choose to trace them 

 to intelligible and real causes. 



The scientist in pronouncing upon causal relations 

 amongst his phenomena, is in danger of committing the 

 logical error of post hoc ergo propter hoc. The fundamental 

 conception of the doctrine of the derivation of species, under 



Trans, viii.~] 31 



