CHAP. VIII.] ESSAYS AT CAMBRIDGE. . 243 



think they see there must be a similar relation between 

 things less known, they reason from the one to the other. 

 This supposes that although pairs of things may differ 

 widely from each other, the relation in the one pair may be 

 the same as that in the other. Now, as in a scientific point 

 of view the relation is the most important thing to know, a 

 knowledge of the one thing leads us a long way towards a 

 knowledge of the other. If all that we know is relation, 

 and if all the relations of one pair of things correspond to 

 those of another pair, it will be difficult to distinguish the 

 one pair from the other, although not presenting a single 

 point of resemblance, unless we have some difference of 

 relation to something else, whereby to distinguish them. 

 Such mistakes can hardly occur except in mathematical and 

 physical analogies, but if we are going to study the consti- 

 tution of the individual mental man, and draw all our 

 arguments from the laws of society on the one hand, or 

 those of the nervous tissue on the other, we may chance to 

 convert useful helps into Wills-of-the-wisp. Perhaps the 

 ' book,' as it has been called, of nature is regularly paged ; 

 if so, no doubt the introductory parts will explain those that 

 follow, and the methods taught in the first chapters will be 

 taken for granted and used as illustrations in the more 

 advanced parts of the course ; but if it is not a ' book ' at 

 all, but a magazine, nothing is more foolish to suppose that 

 one part can throw light on another. 



" Perhaps the next most remarkable analogy is between 

 the principle, law, or plan according to which all things are 

 made suitably to what they have to do, and the intention 

 which a man has of making machines which will work. The 

 doctrine of final causes, although productive of barrenness 

 in its exclusive form, has certainly been a great help 

 to enquirers into nature; and if we only maintain the 

 existence of the analogy, and allow observation to determine 

 its form, we cannot be led far from the truth. 



" There is another analogy which seems to be supplant- 

 ing the other on its own ground, which lies between the 

 principle, law, or plan according to which the forms of 



