James Madison, in a letter to Joseph C. Cabell on October 30, 1828.
A history of that clause, as traced in the printed journal of the Federal Convention, will throw light on the subject.
It appears that the clause, as it originally stood, simply expressed “a power to lay taxes, duties, imposts, and excises,” without pointing out the objects; and, of course, leaving them applicable in carrying into effect the other specified powers. It appears, farther, that a solicitude to prevent any constructive danger to the validity of public debts contracted under the superseded form of government, led to the addition of the words “to pay the debts.”
This phraseology having the appearance of an appropriation limited to the payment of debts, an express appropriation was added “for the expenses of the Government,” &c.
But even this was considered as short of the objects for which taxes, duties, imposts, and excises might be required; and the more comprehensive provision was made by substituting “for expenses of Government” the terms of the old Confederation, viz.: and provide for the common defence and general welfare, making duties and imposts, as well as taxes and excises, applicable not only to payment of debts, but to the common defence and general welfare.
The Writings of James Madison. Edited by Gaillard Hunt. 9 vols. New York: G. P. Putnam’s Sons, 1900–1910.