412 Weismann's Theories — 



activities, present to them all, and capable of reviewing its 

 own states and external objects and events in various orders, 

 cannot itself be multitudinous, but must be as much a unity 

 as anything we can think of. If then we do know any 

 material bodies, any physical force at all, it is simply certain 

 that this principle is neither the one nor the other, but 

 stands out in the strongest contrast with both. Thus since 

 each man knows that it is he who merely feels as well as he 

 who thinks, he knows, if he reflects upon it, that if he has a 

 body, his body and his thinking principle are to his experi- 

 ence one unity — he knows that he is a unity with two sets of 

 faculties, material and mechanical in one aspect, immaterial 

 and non-mechanical in the other aspect. No certainty we 

 can attain to about any other objects can be nearly so certain 

 as this certainty which we have about our own being ; first, 

 its d3mamic, immaterial aspect, and secondly, its material, 

 mechanical aspect. That each man is a material, definitely 

 organised substance in one unity, with a dynamic, immaterial 

 principle of individuation revealed in consciousness, is the 

 first truth of physical science. It is emphatically the funda- 

 mental truth of biological science; for biology deals ex- 

 clusively with living things, and of no living thing can any 

 one have so complete a knowledge as of himself. 



Looking out upon the world about us we find a multitude 

 of living beings, the world of animals, more or less like us, 

 some of them so evidently like us, we cannot but deem it 

 probable that each such being is also the seat of an immaterial, 

 dynamic principle of individuation, however different in kind 

 and in powers it may be from our own. Extending our gaze 

 over nature, we find on all sides of us a network of Hving 

 animal and vegetable forms so like each other, in spite of 

 small gradations of differences, that we cannot well draw a 

 line, and say below it, such living creatures have no such 

 d3niamic individuating principle. 



