CHAP. I.] NATURE AND DESIGN OF THIS WORK. 23 



it is a subjection of some quite distinct kind, is also a matter of 

 deep speculative interest. Further, if the mind is truly deter- 

 mined to be a subject of law, and if its laws also are truly assigned, 

 the question of their probable or necessary influence upon the 

 course of human thought in different ages is one invested with 

 great importance, and well deserving a patient investigation, as 

 matter both of philosophy and of history. These and other 

 questions I propose, however imperfectly, to discuss in the con- 

 cluding portion of the present work. They belong, perhaps, to 

 the domain of probable or conjectural, rather than to that of po- 

 sitive, knowledge. But it may happen that where there is not 

 sufficient warrant for the certainties of science, there may be 

 grounds of analogy adequate for the suggestion of highly pro- 

 bable opinions. It has seemed to me better that this discussion 

 should be entirely reserved for the sequel of the main business of 

 this treatise, which is the investigation of scientific truths and 

 laws. Experience sufficiently instructs us that the proper order 

 of advancement in all inquiries after truth is to proceed from the 

 known to the unknown. There are parts, even of the philosophy 

 and constitution of the human mind, which have been placed 

 fully within the reach of our investigation. To make a due ac- 

 quaintance with those portions of our nature the basis of all en- 

 deavours to penetrate amid the shadows and uncertainties of that 

 conjectural realm which lies beyond and above them, is the 

 course most accordant with the limitations of our present con- 

 dition. 



