Page:Joseph Story, Commentaries on the Constitution of the United States (1st ed, 1833, vol II).djvu/411

 CH. XIV.] been found, that in the usual progress of things the necessities of a nation in every stage of its existence are at least equal to its resources. But, if a more favourable state of things should exist in our own government, still we must expect reverses, and ought to provide against them. It is impossible to foresee all the various changes in the posture, relations, and power of different nations, which might affect the prosperity and safety of our own. We may have formidable foreign enemies. We may have internal commotions. We may suffer from physical, as well as moral calamities; from plagues, famine, and earthquakes; from political convulsions, and rivalries; from the gradual decline of particular sources of industry; and from the necessity of changing our own habits and pursuits, in consequence of foreign improvements and competitions, and the variable nature of human wants and desires. A source of revenue adequate in one age, may wholly or partially fail in another. Commerce, or manufactures, or agriculture may thrive under a tax in one age, which would destroy them in another. The power of taxation, therefore, to be useful, must not only be adequate to all the exigencies of the nation, but it must be capable of reaching from time to time all the most productive sources. It has been observed with no less truth, than point, that "in political arithmetic two and two do not always make four." Constitutions of government are not to be framed upon a calculation of existing exigencies; but upon a combination of these with the probable exigencies of ages, according to the natural and tried course of human affairs. There ought to be a capacity to provide for future contingencies, as they may happen; and as these are (as has been