2 HABIT AND INTELLIGEXCE. 



Impor- than to science, but its importance to science is neverthe- 

 tanceof j^ggg q£ ^j^g gj.g|. magnitude. The first and most essential 



this to * 



scientific condition of scientific progress is the perfect independence 

 piogiesB. ^£ ^j^^ intellect, and its freedom from all authority which 

 cannot justify itself Some sciences, in which the greatest 

 progress has been made, have never been interfered with 

 in their onward progress by any claims whatever on the 

 part of authority. Such has been the case with mathe- 

 matics and with chemistry. Other sciences, as astronomy, 

 geology, and we may now add the sciences of life, of mind, 

 and of language, have been trammelled in their infancy by 

 the shackles of authority, and have been unable to make 

 any great progress until these were cast away. 



But in addition to this independence of authority, some 



of the dominant ideas of the present age in the realm of 



pure science have also been inherited from past centuries. 



Idea of the I speak of the belief that all existence is a domain of law, 



univer-'^ and that nothing is arbitrary : and of that sense of the 



sality of mutual relation of all things which has passed into the 



law, current thought and speech of our time, and is expressed 



in such phrases as "the connexion of the sciences," and 



" the unity and universaKty of the laws of nature." These 



ideas, concerning the universality, the constancy, and the 



uniformity of natural laws, are not in any special sense 



characteristic of either this century or the last. They 



belong to science, and have been confirmed and strengthened 



with the progress of science. But they have taken a far 



stronger hold on the intellects, and I may add on the 



imaginations, of men in this age than they ever did before. 



This is a natural result of the real and great progress made 



by science in this age, not only in the same directions in 



which it was begun by former ages, but also in new 



directions, of which former ages only dreamed. 



The most important step ever taken, in the whole 



history of science, towards establishing this great doctrine 



Newton's of the Unity of law throughout nature, was Newton's dis- 



\'itat"ion'^^ covery of the law of universal gravitation : proving that 



the force which binds the planets in their orbits is the 



same as that which causes a stone to fall to the earth : 



