THE PHILOSOPHICAL BASIS 35 



their meaning, mankind would be lost hopelessly 

 in a wilderness of phenomena ; no continuous 

 progress could be made ; no consistent idea of 

 the world around could ever be attained. Each 

 individual phenomenon, as it appeared time after 

 time, might still be investigated ; but, with his 

 limited mind and short life, no one man could ever 

 secure a basis for adequate knowledge. Without 

 some general way of stating his experiences, he 

 could hand on neither his guesses after truth nor 

 his hard-won information : mankind would never 

 have emerged from barbarism. 



The relations between an observer and his 

 surroundings may for convenience be analysed 

 into the conceptions of length, time, and mass. 

 From these, as we have seen, the other mechanical 

 units can be derived, and a mechanical model of 

 Nature be constructed. It is incomplete ; for 

 even the simplest mechanical fact, such as the 

 fall of a body to the ground, inevitably has 

 other aspects. Heat may be developed, electrical 

 manifestations appear, and, if the body be a living 

 one, physiological and psychological changes take 

 place. Neglecting these aspects, however, a com- 

 plete mechanical account of the phenomenon can 

 be given in terms of the three fundamental concep- 

 tions. As we have seen, new ideas, which may be 

 derived from the primary ones, become necessary 

 in the course of the investigation. The body falls 

 with a certain acceleration, and, at any instant, is 

 moving with a definite velocity. As it falls, it 

 acquires energy of motion and loses energy of 

 position. 



During the fall we find that we can success- 



