308 Relation of Use and Disuse to Evolution 



people ought to start out with an improved intellectual 

 mechanism, but not necessarily with the direct result of 

 learning, or increased knowledge. The horse that has been 

 trained should give birth to swifter colts. An animal that 

 has recovered from an infectious disease should have more 

 resistant offspring. 



From the point of view of logic, nothing could be more 

 plausible. Indeed, Herbert Spencer and other supporters 

 of Lamarckism laid the greatest stress upon this. No theory 

 could more simply explain the facts, the actual fitness of 

 living species to the conditions under which they live, to 

 the getting of food, to the escaping from enemies, to the 

 resisting of cold or heat, to the finding of mates, to the 

 shielding of the young, and so on. The whole world of life 

 does in fact behave in every way as if each individual born 

 brought with him as part of his innate equipment the very 

 qualities and capacities that a mature individual seems to 

 acquire in the course of his experience with the environ- 

 ment. The theory is sound, argues Spencer, since ( i ) it 

 explains adequately the observed facts; and since (2) evo- 

 lution of forms with progressive adaptation is otherwise 

 inconceivable. In other words, it must be true because it 

 stands to reason, and because without this idea we are at a 

 loss to understand what happens. 



'Postulates versus Facts 



It needs repeatedly to be pointed out that although 

 much of our reasoning is of precisely this form, it is utterly 

 unreliable as a means of discovering the truth. We can all 

 recognize the fallacy in primitive myth and current super- 

 stition, when they take this form. Sol must drive his chariot 

 over to the east during the night, otherwise the sun could 

 not rise the next day. Ghosts must consist of material 

 substance, otherwise we could not see them. A magnet must 

 have intelligence, otherwise it could not know iron filings 

 from sawdust. The earth must be flat, otherwise things 



