" Of all truths relating to phenomena, the most valuable to us are those which 

 relate to the order of their succession. On a knowledge of these is founded 

 every reasonable anticipation of future facts, and whatever power we possess 

 of influencing those facts to our advantage. Even the laws of geometry are 

 chiefly of practical importance to us as being a portion of the premises from 

 which the order of the succession of phenomena may be inferred." 



JOHN STUART MILL. 



BEGUN in the autumn of the year 1845, without the cognizance, 

 or at the suggestion of a single human being, the present Trans- 

 lation is due to the fact of its original having encountered a some- 

 what kindred spirit, and aroused therein the desire to render others 

 participant, if possible, in the large amount of instruction it is so 

 well calculated to afford. And now that the work is done, what 

 remains for the labourer at second-hand to say by way of preamble 

 to his newly-dressed wares? Had the book been printed within 

 the pale of a philosophical or physico-theological sect, the Trans- 

 lator's final duty would have been clearly enough prescribed. 

 Already bound to the profession of " particular tenets," his main 

 object would be to indulge in a laudatory but servile abstract of his 

 author's doctrines, or, if having set out with the expressed inten- 

 tion of illustrating their bearings upon the state of science past, 

 present, and to come, he would become so drunk beforehand with 

 the large and unbridled potation of his creed, as to surprise the 

 casual reader by informing him that such an intention is useless, for 

 the two stand in direct antithesis to each other. Examples of this 

 mode of procedure are not wanting at the present day, whether at 

 home or abroad. They are the produce of that spirit, which, rife 

 enough in the Middle Ages, has been so graphically described by 

 Professor \\Tiewell under the title of the "Comrnentatorial," and 

 " whose professed object is to explain, to enforce, to illustrate doc- 

 trines assumed to be true, but not to obtain additional truths or new 

 generalizations." While from dealings of this character, as being 

 utterly opposed to the sacred cause of Truth, I turn away with 

 feelings of repugnance, to which the lessons of some personal 

 experience have lent their aid, it is not my business, upon the other 



