524 LOGIC OF THE MORAL SCIENCES. 



always makes them so : that an interest on one side 

 of a question tends to bias the judgment ; not that 

 it invariably does so : that experience tends to give 

 wisdom; not that such is always its effect. These 

 propositions, being assertive only of tendencies, are not 

 the less universally true because the tendencies may 

 be counteracted. 



$ 5. While on the one hand Psychology is alto- 

 gether, or principally, a science of observation and 

 experiment, Ethology, as I have conceived it, is, as I 

 have already remarked, altogether deductive. The 

 one ascertains the simple laws of Mind in general, the 

 other traces their operation in complex combinations 

 of circumstances. Ethology stands to 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 very proper place for a logical 

 remark, which, though of general application, is of 

 peculiar importance in reference to the present subject. 

 Bacon has judiciously observed that the axiomata 

 media of every science principally constitute its value. 

 The lowest generalizations, until explained 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 



