The subject matter of Public Finance is of such a nature that its study cannot be separated from that of other sciences. Students of the subject must take frequent excursions into the related fields of Political Science, History, Sociology, and Ethics. Likewise, those who are primarily interested in these related subjects find that account must be taken of the workings of the principles of Public Finance.

Relation to Political Science and History. - The principles which underlie a study of expenditures and revenues have a dependence upon Political Science second only to that which they have upon Economics. The form of government under which the citizens live and the officials work is of the utmost importance. Differences in the method of conducting fiscal affairs would necessarily be found in states of autocratic, democratic, socialistic, or individualistic governmental tendencies. Many political restraints exist, also, either because of constitutional or legislative provisions, which must always be taken into consideration by the fiscal student or official. In the United States, for example, a tax would not be levied upon exports because of constitutional restrictions to that effect. Political expediency, moreover, is often so important in fiscal matters that it takes precedence over the soundness of economic principles which might be applied. Revenues must be had quickly, at times, and that method is used which will supply the needed funds, notwithstanding the economic objections which might be raised.

The interest in Political Science cannot be separated from the principles of Public Finance. Revenues must be secured to carry out the policies of executives and legislators. Many of the compromises which have been written into constitutions and statutes have been formulated by fiscal considerations. Officials must always be concerned about the exaction and use of funds, for there is no surer and quicker method for gaining the disfavor of a constituency than through the misuse of public revenues.

That would be a poor fiscal policy which took no consideration of the activities of the past, with their resulting successes or failures. A study of history, consequently, is an invaluable asset in helping to formulate modern fiscal policies. Countries have different characteristics, their citizens have peculiar traits, and it is only by a study of history that these can be properly interpreted. It is because of these inherent differences that a successful system for obtaining revenues in one country would absolutely fail to give satisfaction in another. The student of history, moreover, can be no less interested in what Public Finance has to offer. In tracing revolutions and constitutional reforms, for example, he will frequently find that fiscal considerations have had an important influence, if, indeed, not an overwhelming one.

Relation to Sociology and Ethics. - The problems of social reform and those of Public Finance are, at present, inseparably related. No longer is the individual held entirely responsible for bettering social conditions, but the various governmental units have adopted this activity as one of their primary functions. So extensively have they entered this field that one of the largest single items of expenditure is for the classes of delinquents, defectives, and dependents. The enormous sums which are spent annually upon social institutions are of vital interest to the students of expenditures and revenues. The student of sociology is no less interested. He must be concerned with the results of government activities of this nature, and compare these results with what has been accomplished through other avenues of endeavor.

Ethical considerations must not be omitted from the discussion and formulation of fiscal principles. When the burden of a tax does not rest where it is placed, but is shifted on to some one else, the question of justice immediately presents itself. The same question also arises when proposals are made to tax some individuals or classes at a higher rate than others. The fiscal system is frequently called upon to help solve the problem of evil through the regulation or elimination of undesirable industrial or social institutions. Examples of this are the use of taxes to eliminate the circulation of state bank notes, and to regulate the use of intoxicating liquors. It is clearly demonstrated, then, that Public Finance is far from being an independent science, but draws heavily from other fields as well as supplies much material to them.