and its power of accurate prediction. The precision of scientific conclusions usually varies inversely with the complexity of the factors involved, that is, a complex science can state laws only hypothetically and can predict future events only with reservations. It is sometimes argued that a body of knowledge deserves to be called a science only in proportion to its ability to predict with accuracy; but such limits would be too narrow. A body of knowledge should be called a science if the material can be classified and cause and effect be demonstrated. After that stage is reached accuracy in prediction in the various sciences is merely a difference of degree and not of kind. The astronomer can work out the orbit of a comet and redict with great precision the return of that comet. But he does so with the assumed qualifications that no force intervenes in the meantime to change its orbit. In the same way the social scientist may work out the nature of a particular force, or even a combination of forces, and predict the results provided no new influence intervenes. But the difference in the nature of the two predictions is that, while the astronomer is reasonably certain that no new influence will appear to disturb his calculations, the sociologist knows well that before long some disturbing factor, such as a legislature, or a new invention, will intervene to alter the original conditions. Because of this complexity of factors the social sciences are sometimes called hypothetical; and prediction with them simply means an indication of the effects of the action of given forces. It does not imply that conditions may not change and that hence these effects may not be altered in the course of time. To conclude however that a hypothetical science is of no practical value would be far from the truth. The function of the social sciences consists in ascertaining the nature of particular forces and, so far as possible, the results of several forces working together. It is impossible to direct social evolution intelligently or employ social forces to advantage, unless they are first understood.

Sociology Deals with Uniformities. Certain critics profess an inability to believe in the possibility of a science of society simply because the subject matter deals with human beings who are free agents, whose actions therefore, they maintain, can neither be predicted nor be reduced to laws. Fortunately for the sociologist the question of free will and determinism does not have to be settled, before social phenomena are studied, for these terms merely indicate methods of explaining human conduct which may be left to philosophers to decide. The sociologist simply accepts the evident fact of uniformities in human actions without explaining the psychological causes of those uniformities. The fact that men act similarly under like conditions is demonstrated over and over again by statistics. The most obvious are those of the birth and death rates which are comparatively unvarying unless some new factor enters. But, if statistics of this kind are objected to as proof of uniformity in human action on the ground that such phenomena are not always subject to human volition, it may be pointed out that the marriage rate is more uniform than the birth rate and the suicide rate in a given district is as invariable as the total death rate. If then human actions can be reduced to uniformities, they are a possible subject matter for a science, whatever the explanation may be of the psychological causes of those actions.

Subdivisions of Sociology. Sociology as a science is so broad, and the subject matter so complicated, that it may easily be divided into parts, and it may be presented from different angles. The psychological side of human relations may be specially emphasized; or the material side, that is the physical and biological aspects of social phenomena, may be made the point of approach. At the present time the psychological aspect of society is given prominence by several writers; and this phase is undoubtedly important, especially in this early period of the development of the science. Social psychology may however properly be separated from sociology as a subject in itself, standing intermediate between psychology and sociology proper, and forming an indispensible connecting link.

Comte, and a few later writers also, have divided the subject into static and dynamic sociology; and such a distinction is a possible one. According to this division dynamic sociology would deal with social progress. Its point of view would be the long range one; and it would analyze those factors and forces that cause changes in social conditions and improvements in social life. Static sociology, on the other hand, would study a cross section of society at any given time, but presumably the present period. It would investigate the social institutions existing, their proper functions, and their relations to other institutions and to social life in general. For example, a study of the church as a social organization and of its proper function among other organizations would belong to static sociology. On the other hand a study of the development of an institution, like the family, and the causes of that development would be a problem of dynamic sociology. It must be admitted that these two points of view are not wholly distinct. Problems in one division naturally lead to problems in the other. A study of the proper function of any social organization naturally leads to problems of the perfecting of that organization, that is to the problem of its development. However, although a complete knowledge of society would involve an understanding of both the static and dynamic aspects of the subject, it is quite possible, perhaps even necessary, to present these divisions separately; and this book will deal primarily with the laws of progress rather than with the problems of present day institutions.

Sociology may now be defined as the science which treats of the organization and development of human societies. Dynamic sociology treats of the laws of social development; and static sociology deals with the structure of society and with the nature and proper functions of its institutions.

Progress Distinguished from Other Forms of Social Change. Before entering upon the discussion of the principles of social progress, it will be advisable to define the meaning of the term progress and also to consider some of the misconceptions which may arise from its use. Progress is commonly understood to mean an approach towards the ideal. It implies an ultimate, if not a continuous, increase in well-being. But not all change is progress. Some changes are the opposite of progress and mean retrogression or dissolution. Progress itself includes two forms of improvement, which may be distinguished by the same terms used to describe similar processes in lower

organic life, evolution and growth. Evolution refers to the development of higher types out of lower, while growth describes the developmental changes which the individual undergoes in his life process. Occasionally among vegetable or animal forms of life a new species appears and persists. Such a variant may be superior to pre-existing forms and contribute to true progress; but not always. New species have not arisen out of the old in uninterrupted progression. Sometimes new forms are inferior in organization, or they may even be parasitic; and in such cases no gain is discernible. Growth is clearly a different process. A seed germinates and develops into a mature plant, deteriorates and dies. And a host of similar plants follow the same course without producing superior forms. Growth is of course essential and desirable, but it is quite distinct from the process of evolution, though it may perhaps merely represent a shorter rhythm or pulsation of life forces.

In the sphere of social life similar distinctions can be made. New and superior types of organization occasionally appear, as for example, the monogamic form of the family, or a democratic form of government springing from an autocratic form. But in contrast to the emergence of a new type, a particular organization goes through a process of growth from a small beginning without change in its fundamental characters. For example, a municipality begins with a small population and a simple organization; and, as population increases, buildings multiply and become more varied, streets are improved, and transportation and lighting systems are perfected. But all these improvements indicate mere growth, like that of youth to manhood, rather than the evolution of a new type. The city resembles scores of other cities all of which have passed through similar transformations. Such changes in social organizations must be classed as phases of progress but not of evolution.

Another phenomenon, quite common in human societies, is the diverse developments which the same institution may undergo in different societies or environments. Just as a plant may alter its appearance because of modifications in soil or climate, so a social institution may be altered when borrowed by an alien people. The parliamentary form of government is quite a different institution in continental countries from what it is in England, the country of its origin. Religions almost always undergo marked changes both in form and in content as they are adopted by peoples in different stages of culture. Such modifications are not in themselves either marks of progress or of retrogression. They may, however, be the beginnings of variations leading to improvements or even to the evolution of new types.

Next, all forms of change indicating degeneration must be distinguished from constructive changes making for progress. In the social sense disease may be defined as a condition which impedes normal growth, or keeps the social organs from performing their proper functions. This phase of social life has not yet been sufficiently studied to be fully recognizable. We are likely to look upon everything which is undesirable as social disease; but we should remember that mere growth and progress as such necessarily involve waste and elimination; and, disagreeable as this side of social life may be, it is not abnormal and cannot be remedied. A certain amount of poverty, crime, and degeneracy is doubtless the normal by-product of progress. Disease should be cured, and if possible eradicated; but time and energy should not be wasted in attacking without discrimination everything which appears unworthy and unpleasant.

Finally, there is a possibility that a further difficult distinction between the normal and the abnormal may have to be made. In case of individual organisms dissolution and death are inevitable after the cycle of life is completed. In the individual therefore old age itself with its various weaknesses is not abnormal. Is a similar stage of senescence and decrepitude normal with human societies? If so, then the weaknesses and disabilities of this stage must again be distinguished from disease which is curable. However, opinions differ greatly on this point. It is not at all certain that death is a natural phenomenon in the case of societies. Institutions certainly decline, and societies disappear; but it is possible that such phenomena are always due to abnormal conditions, and no distinction along this line will be found necessary.

The distinctions made here between evolution, growth, and