If this correctly represents Hamilton's position, he is no conservative hero.
[The quotes below in blue are all from Treasury Secretary Hamilton's 1791 Report on the Subject of Manufactures to the House of Representatives.]
Hamilton believed that the "general welfare" clause in Article I, Section 8 provided the Congress with authority that was not confined to the other, more specific grants of power itemized in that same section:
"A question has been made concerning the constitutional right of the government of the United States to apply this species of encouragement, but there is certainly no good foundation for such a question. The national legislature has express authority ``To lay and Collect taxes, duties, imposts and excises, to pay the debts and provide for the common defense and general welfare'' with no other qualifications than that ``all duties, imposts and excises, shall be uniform throughout the United States, that no capitation or other direct tax shall be laid unless in proportion to numbers ascertained by a census or enumeration taken on the principles prescribed in the Constitution,'' and that ``no tax or duty shall be laid on articles exported from any state.'' These three qualifications excepted, the power to raise money is plenary, and indefinite; and the objects to which it may be appropriated are no less comprehensive, than the payment of the public debts and the providing for the common defense and ``general welfare.'' The terms ``general welfare'' were doubtless intended to signify more than was expressed or imported in those which preceded; otherwise numerous exigencies incident to the affairs of a nation would have been left without a provision. The phrase is as comprehensive as any that could have been used; because it was not fit that the constitutional authority of the Union, to appropriate its revenues should have been restricted within narrower limits than the ``general welfare'' and because this necessarily embraces a vast variety of particulars, which are susceptible neither of specification nor of definition."
And who did Hamilton believe was constitutionally empowered to decide what is meant by the term "general wefare"? The Congress:
"It is therefore of necessity left to the discretion of the national legislature, to pronounce, upon the objects, which concern the general welfare, and for which under that description, an appropriation of money is requisite and proper. And there seems to be no room for a doubt that whatever concerns the general interests of learning of agriculture, of manufactures, and of commerce are within the sphere of the national councils as far as regards an application of money."
Hamilton felt that the only Constitutional limitation on the power to spend for the "general welfare" concerned the geographical requirement that the program be applicable throughout the entire country:
"The only qualification of the generality of the phrase in question, which seems to be admissible, is this--That the object to which an appropriation of money is to be made be general and not local; its operation extending in fact, or by possibility, throughout the Union, and not being confined to a particular spot."
"No objection ought to arise to this construction from a supposition that it would imply a power to do whatever else should appear to Congress conducive to the general welfare. A power to appropriate money with this latitude which is granted too in express terms would not carry a power to do any other thing, not authorized in the Constitution, either expressly or by fair implication."