That's very interesting..... and makes way too much sense!
No, actually, it doesn't make sense.
One of the first rules of thumb in law is that if you think a word, phrase, or clause in a law (and the Constitution is itself the highest law of the land) has no meaning, then you're reading it wrong. Phrases aren't thrown into laws just for color, they're there because they were intended to invoke some legal effect.
Article 1, Section 8 says that Congress shall have the power to use public monies "to provide for the general welfare" because, by gosh, it intends for Congress to have the power to spend money on the general welfare.
Additionally, would you actually want Congress to *NOT* have the power to spend a dime on anything that provides for the general welfare of the country, *except* for defense purposes *only*? That'd be crazy.
But specifically addressing the notion that "If there were a general welfare power, then why bother to enumerate a bunch of specific powers in the same Section", this question overlooks several key and critical points.
1. The "general welfare power" is not an "all-inclusive do anything they want in the general welfare power" -- it only authorizes *SPENDING* on the general welfare, NOT any other actions which might promote the general welfare.
2. The other parts of Article 1, Section 8 (i.e. clauses 2-18) have to do with ENFORCEMENT powers -- things the federal government is authorized to COMPELL states or individuals to do, or PROHIBIT them from doing (by force of law), or ENGAGE IN as a federal action (like run the post offices, for example).
3. Spending places no such obligation on anyone; whether someone or some group gets paid by the federal government to do some job or provide some service is *voluntary*, while the power granted in the rest of Article 1, Section 8 are enumerated powers of *compulsion*.
4. This is why the "compulsive powers" are put on a very strict leash and thus specifically enumerated, while the spending power in Clause 1 is less specified and stated more broadly.
5. This is also why the enumerated powers in Clauses 2-18 (and the first half of Clause 1, concerning the power to force tax collections) do not in any way overlap the nonenumerated, noncompulsive *spending* powers granted in the second half of Clause 1. This is why it's *not* illogical for there to simultaneously be a "general welfare" *spending* power, *and* enumerated "controlling" powers in "the same section".
And interesting -- and in my experience, unique -- analysis of the issue. I don't find your reasoning persuasive (the "spending vs. coercion" distinction) but no matter. Many people, some of them rather illustrious like Hamilton, would support your conclusion. But it seems to me that your conclusion is contrary to the "small, weak" government which was the generally-popular idea at the time of the Convention. Anyway, there were probably people with your opinion and those with mine at the very beginning. As there are today. And as there will be tomorrow.
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 defense 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 defense or general welfare. No stronger proof could be given of the distress under which these writers labor for objections, than their stooping to such a misconstruction.Had no other enumeration or definition of the powers of the Congress been found in the Constitution, than the general expressions just cited, the authors of the objection might have had some color for it; though it would have been difficult to find a reason for so awkward a form of describing an authority to legislate in all possible cases. A power to destroy the freedom of the press, the trial by jury, or even to regulate the course of descents, or the forms of conveyances, must be very singularly expressed by the terms "to raise money for the general welfare."
But what color can the objection have, when a specification of the objects alluded to by these general terms immediately follows, and is not even separated by a longer pause than a semicolon? If the different parts of the same instrument ought to be so expounded, as to give meaning to every part which will bear it, shall one part of the same sentence be excluded altogether from a share in the meaning; and shall the more doubtful and indefinite terms be retained in their full extent, and the clear and precise expressions be denied any signification whatsoever? For what purpose could the enumeration of particular powers be inserted, if these and all others were meant to be included in the preceding general power? Nothing is more natural nor common than first to use a general phrase, and then to explain and qualify it by a recital of particulars. But the idea of an enumeration of particulars which neither explain nor qualify the general meaning, and can have no other effect than to confound and mislead, is an absurdity, which, as we are reduced to the dilemma of charging either on the authors of the objection or on the authors of the Constitution, we must take the liberty of supposing, had not its origin with the latter.
The objection here is the more extraordinary, as it appears that the language used by the convention is a copy from the articles of Confederation. The objects of the Union among the States, as described in article third, are "their common defense, security of their liberties, and mutual and general welfare." The terms of article eighth are still more identical: "All charges of war and all other expenses that shall be incurred for the common defense or general welfare, and allowed by the United States in Congress, shall be defrayed out of a common treasury," etc. A similar language again occurs in article ninth. Construe either of these articles by the rules which would justify the construction put on the new Constitution, and they vest in the existing Congress a power to legislate in all cases whatsoever. But what would have been thought of that assembly, if, attaching themselves to these general expressions, and disregarding the specifications which ascertain and limit their import, they had exercised an unlimited power of providing for the common defense and general welfare? I appeal to the objectors themselves, whether they would in that case have employed the same reasoning in justification of Congress as they now make use of against the convention. How difficult it is for error to escape its own condemnation!
-- Final paragraphs of The Federalist No. 41, attributed to Madison.