To illustrate empirically of what wide application the concept of Series is, and how it is present wherever the concept of Law is present, and vice versa, is useful in beginning a discussion of this category, although anything like present completeness in such illustrations is hopeless. You find serial order wherever you look in the world of definitely conceived or of exactly describable fact. Space and Time illustrate our principle in their every detail. They and the Number-Series are the most familiar of the forms in which serial order appears to us. As for more special classes of instances, I conceive my own life as a particular and connected series of events, and yours in the same way. All the more significant social relations involve, directly or indirectly, the establishment of serial order-systems such as those of debtors and creditors, of friends and neighbors, of fellow-citizens, of teachers and pupils, of official superiors and inferiors, of the various grades of relationships in families, and so on indefinitely. For a social relationship of the type of debtor, friend, neighbor, fellow-citizen, teacher, superior, ancestor, cousin, has the logical character illustrated by saying that if A stands in this relation to B, B may, and frequently does, stand in the same relationship to C, C to D, and so on, — the collection of social individuals A, B, C, constituting in this way an ordered series, sometimes of a very limited, but more often of a very widely extended scope. In natural history, the classification of living forms, the study of the structures and functions of organisms, the accounts of the evolution and decay of all types of life, involve the conception of ordered series. Geology, on its descriptive side, is similarly a science of
