It may still be useful to advert to the three principal cases into which Classification may be resolved; 1, that of objects considered as synchronical; 2, that of objects considered as successive; 3, that of feelings. The first is exemplified in the common classes of sensible objects, as men, horses, trees, and so on; and requires no further explanation. The second is exemplified in the classes of events, denoted by such words, as Birth, Death, Snowing, Thundering, Freezing, Flying, Creeping. By these words there is always denoted one antecedent and one consequent, generally more, sometimes a long train of them. And it is obvious that each of them is, at once, the name of each instance individually, and of all taken generally together. Thus, Freezing, is not the name of an individual instance of freezing only, but of that and of all other instances of Freezing. The same is the case with other words of a still more general, and thence more obscure signification, as Gravitation, Attraction, Motion, Force, &c.; which words have this additional source of confusion, that they are {270} ambiguous, being both abstract and concrete. When we say that there is a third case of classification, relating to Feelings, it does not mean that the two former do not relate to feelings: for when we say, that we classify objects, as men, horses, &c.;--or events, as the sequences named births, deaths, and so on;--it is obvious that our operation is about our own feelings, and nothing else; as the objects, and their successions, are, to us, the feelings merely which we thus designate. But as there are feelings which we do thus designate; and feelings which we do not; it is convenient, for the purpose of teaching, to treat of them apart. The Feelings, of this latter kind, which we classify, are either single feelings, or trains. Thus, Pain is the name of a single feeling, and the name both of an individual instance, and of indefinite instances, forming a most extensive class. Memory is the name not of a single feeling or idea, but of a train; and it is the name not only of a single instance, but of all instances of such a train, that is, of a class. The same is the case with Belief. It is the name of a train consisting of a certain number of links; and it is the name not only of an individual instance of such trains, but of all instances, forming an extensive class. Imagination is another instance of the same sort of classification. So also is Judgment, and Reasoning, and Doubting, and we might name many more.