424 THE PRINCIPLES OF SCIENCE. 



of definition. Tastes of mixed or intermediate character 

 may exist almost ad infinitum, and, what is still more 

 troublesome, the tastes clearly united within one class 

 may differ more or less from each other, without our being 

 able to arrange them in subordinate genera and species. 

 The same remarks may be made concerning the classifi- 

 cation of odours, which may be roughly grouped according 

 to the arrangement of Linnaeus as, Aromatic, Fragrant, 

 Ambrosiac, Alliaceous, Fetid, Virulent, Nauseous. Within 

 each of these vague classes, however, there would be 

 infinite shades of variety, and each class would graduate 

 probably into each other class. The varieties of odour 

 which can be discriminated by an acute olfactory organ 

 are almost infinite ; every rock, stone, plant, or animal 

 has some slight odour, and it is well known that dogs, or 

 even blind human beings, can discriminate persons by a 

 slight distinctive odour which usually passes unnoticed. 



Nearly similar remarks may be made concerning the 

 higher feelings of the human mind, usually called emotions. 

 We know what is anger, grief, fear, hatred, love ; and 

 many systems for classifying these feelings have been 

 proposed at one time or another. They may be roughly 

 distinguished according as they are pleasurable or painful, 

 prospective or retrospective, selfish or sympathetic, active 

 or passive, and possibly in many other ways, but each 

 mode of arrangement will be indefinite and unsatisfactory 

 when followed into details. As a general rule, the emo- 

 tional state of the mind at any moment will be neither 

 pure anger nor pure fear, nor any one pure feeling, but 

 an indefinite and complex aggregate of feelings. It may 

 be that the state of mind is really a sum of several distinct 

 modes of agitation, just as a mixed colour is the sum of 

 the several distinct rays of the spectrum. In this case 

 there may be more hope of some method of analysis being 

 successfully applied at some future time. But it may 



