276 THE GRAMMAR OF SCIENCE 



regulate our mechanism so as to describe our past and 

 predict our future experience. This how of motion is 

 the point to which we must next turn. The laws of 

 motion in the widest sense embrace all physical science — 

 perhaps it were not too much to say all science whatever. 

 All laws, von Helmholtz tells us, must ultimately be 

 merged in laws of motion. Even such a complex pheno- 

 menon as that of heredity is at bottom, Haeckel holds, a 

 transference of motion. Strong in her power of describ- 

 ing hoiv changes take place, Science can well afford to 

 neglect the why. She may not, so long at least as 

 psychology stands where it does, go as far as to fully 

 accept even Emil du Bois-Reymond's second Ignorabimus ; 

 but as to what consciousness is and why there is a 

 routine of sense-impressions she is content for the present 

 to say, " Ignoramus^ 



SUMMARY 



The notion of matter is found to be equally obscure whether we seek for 

 definition in the writings of physicists or of " common-sense " philosophers. 

 The difficulties with regard to it appear to arise from asserting the 

 phenomenal but imperceptible existence of conceptual symbols. Change of 

 sense-impression is the proper term for external perception, motion for our 

 conceptual symbolisation of this change. Of perception the questions " what 

 moves " and " why it moves " are seen to be idle. In the field of conception 

 the moving bodies are geometrical ideals with merely descriptive motions. 



Of the du Bois-Reymonds' three cries of Ignorabimus, only the second in 

 a modified sense is scientifically valuable, the others are unintelligible, 

 because we find that matter, force, and "action at a distance" are not terms 

 which express real problems of the phenomenal world. 



LITERATURE 



Bois-Reymond, Emil du. — Ueber die Grenzen des Naturerkennens. 



Leipzig, 1876. 

 Clerk-Maxwell, J. — Articles "Atom" and "Ether" in the Encyclopaedia 



Britannica, reprinted in the Scientific Papers, vol. ii. pp. 445 and 763. 



The article on the " Constitution of Bodies " may also be consulted with 



advantage. 

 Clifford, W. K. — Lectures and Essays, vol. i. ("Atoms" and "The 



Unseen Universe"). London, 1879. 



