456 LOGIC OF THE MORAL SCIENCES. 



Psychology in a relation very similar to that in which the 

 various branches of natural philosophy stand to mechanics. 

 The principles of Ethology are properly the middle principles, 

 the axiomata media (as Bacon would have said) of the science 

 of mind : as distinguished, on the one hand from the empirical 

 laws resulting from simple observation, and on the other from 

 the highest generalizations. 



And this seems a suitable place for a logical remark, which, 

 though of general application, is of peculiar importance in 

 reference to the present subject. Bacon has judiciously ob- 

 served that the axiomata media of every science principally 

 constitute its value. The lowest generalizations, until ex- 

 plained by and resolved into the middle principles of which 

 they are the consequences, have only the imperfect accuracy 

 of empirical laws ; while the most general laws are too general, 

 and include too few circumstances, to give sufficient indication 

 of what happens in individual cases, where the circumstances 

 are almost always immensely numerous. In the importance, 

 therefore, which Bacon assigns, in every science, to the middle 

 principles, it is impossible not to agree with him. But I con- 

 ceive him to have been radically wrong in his doctrine re- 

 specting the mode in which these axiomata media should be 

 arrived at ; though there is no one proposition laid down in 

 his works for which he has been more extravagantly eulogized. 

 He enunciates as an universal rule, that induction should pro- 

 ceed from the lowest to the middle principles, and from those 

 to the highest, never reversing that order, and consequently 

 leaving no room for the discovery of new principles by way of 

 deduction at all. It is not to be conceived that a man of his 

 sagacity could have fallen into this mistake, if there had 

 existed in his time, among the sciences which treat of suc- 

 cessive phenomena, one single instance of a deductive science, 

 such as mechanics, astronomy, optics, acoustics, &c. now are. 

 In those sciences it is evident that the higher and middle 

 principles are by no means derived from the lowest, but the 

 reverse. In some of them the very highest generalizations 

 were those earliest ascertained with any scientific exactness ; 

 as, for example (in mechanics), the laws of motion. Those 



