INTRODUCTION. 19 



ideas, there is, in the natural series of speculation, 

 no self-correcting principle. A philosophy con- 

 structed on notions obscure, vague, and unsub- 

 stantial, and held in spite of the want of corre- 

 spondence between its doctrines and the actual train 

 of physical events, may long subsist, and occupy 

 men's minds. Such a philosophy must depend for 

 its permanence upon the pleasure which men feel 

 in tracing the operations of their own and other 

 men's minds, and in reducing them to logical con- 

 sistency and systematical arrangement. 



In these cases the main subjects of attention are 

 not external objects, but speculations previously 

 delivered ; the object is not to interpret nature, but 

 man's mind. The opinions of the masters are the 

 facts which the disciples endeavour to reduce to 

 unity, or to follow into consequences. A series of 

 speculators who pursue such a course, may properly 

 be termed a School, and their philosophy a School 

 Philosophy; whether their agreement in such a 

 mode of seeking knowledge arise from personal 

 communication and tradition, or be merely the 

 result of a community of intellectual character and 

 propensity. The two great periods of School Phi- 

 losophy (it will be recollected that we are here 

 directing our attention mainly to physical science), 

 were that of the Greeks and that of the Middle 

 Ages; the period of the first waking of science, and 

 that of its mid-day slumber. 



C2 



