Constitution. I will address one additional reflection, only, to those who contend that the power ought to have been restrained to external taxation—by which they mean, taxes on articles imported from other countries. It cannot be doubted, that this will always be a valuable source of revenue; that for a considerable time, it must be a principal source; that at this moment, it is an essential one. But we may form very mistaken ideas on this subject, if we do not call to mind in our calculations, that the extent of revenue drawn from foreign commerce must vary with the variations, both in the extent and the kind of imports; and that these variations do not correspond with the progress of population, which must be the general measure of the public wants. As long as agriculture continues the sole field of labor, the importation of manufactures must increase as the consumers multiply. As soon as domestic manufactures are begun by the hands not called for by agriculture, the imported manufactures will decrease as the numbers of people increase. In a more remote stage, the imports may consist in a considerable part of raw materials, which will be wrought into articles for exportation, and will, therefore, require rather the encouragement of bounties, than to be loaded with discouraging duties. A system of Government, meant for duration, ought to contemplate these revolutions, and be able to accommodate itself to them.
Some, who have not denied the necessity of the power of taxation, have grounded a very fierce attack against the Constitution, on the language in which it is defined. It has been urged and echoed, that the power "to lay and collect taxes, duties, imposts, and excises, to pay the debts, and provide for the common defence and general welfare of the United States," amounts to an unlimited commission to exercise every power, which may be alleged to be necessary for the common defence