One of the most disputed questions in political science and in practical statesmanship relates to the proper limits of the functions and agency of governments. It may be agreed that they fall into two classes: functions which are either inseparable from the idea of government or are exercised habitually by all governments; and those respecting which it has been considered questionable whether governments should exercise them or not. The former may be termed the necessary, the latter the optional, functions of government.
It may readily be shown that the admitted functions of government embrace a much wider field than can easily be included within the ring-fence of any restrictive definition, and that it is hardly possible to find any ground of justification common to them all, except the comprehensive one of general expediency; nor to limit the interference of government by any universal rule, save the simple and vague one that it should never be admitted but when the case of expediency is strong.
A most important consideration in viewing the economical effects arising from performance of necessary government functions is the means adopted by government to raise the revenue which is the condition of their existence.
The qualities desirable in a system of taxation have been embodied by Adam Smith in four maxims or principles, which may be said to have become classical:
(1) The subjects of every state ought to contribute to the support of the government as nearly as possible in proportion to their respective abilities; that is, in proportion to the revenue which they respectively enjoy under the protection of the state.
(2) The tax which each individual has to pay ought to be certain, and not arbitrary. A great degree of inequality is not nearly so great an evil as a small degree of uncertainty.
(3) Every tax ought to be levied at the time or in the manner in which it is most likely to be convenient for the contributor to pay it. Taxes upon such consumable goods as are articles of luxury are all finally paid by the consumer, and generally in a manner that is very convenient to him.
(4) Every tax ought to be so contrived as to take out and keep out of the pockets of the people as little as possible over and above what it brings into the public treasury.
Taxes on commodities may be considered in the following way. Suppose that a commodity is capable of being made by two different processes. It is the interest of the community that of the two methods producers should adopt that which produces the best article at the lowest price. Suppose, however, that a tax is laid on one of the processes, and no tax at all, or one of lesser amount, on the other. If the tax falls, as it is, of course, intended to do, upon the process which the producers would have adopted, it creates an artificial motive for preferring the untaxed process though the inferior of the two. If, therefore, it has any effect at all it causes the commodity to be produced of worse quality, or at a greater expense of labour; it causes so much of the labour of the community to be wasted, and the capital employed in supporting and remunerating the labour to be expended as uselessly as if it were spent in hiring men to dig holes and fill them up again. The loss falls on the consumers, though the capital of the country is also eventually diminished by the diminution of their means of saving, and in some degree of their inducements to save.
Taxes on foreign trade are of two kinds: taxes on imports and on exports. On the first aspect of the matter it would seem that both these taxes are paid by the consumers of the commodity. The true state of the case, however, is much more complicated.