Federalist 45 provides us with critical information regarding the history, purpose, and constitutional definition, necessary authority, and the delineation of Federalism.
In Federalist 45, Madison argues that the Union as outlined in the Constitution is necessary to the people’s happiness and that the balance of power between the states and the national government will support the greatest happiness for the people. He argues that the primary purpose of government, and hence of the Constitution, is the people’s happiness, and therefore only a government that promotes the people’s happiness is legitimate, writing, “Were the plan of the Convention adverse to the public happiness, my voice would be , reject the plan. Were the Union itself inconsistent with the public happiness, it would be, abolish the Union”.
Founders Online: The Federalist Number 45, [26 January] 1788
The Tenth Amendment is largely ignored today, as politicians all too conveniently assert that Congress has unlimited powers in pursuit of "the general welfare." They're wrong. James Madison, the principal architect of the Constitution, stated in Federalist 45 (written during the ratification process) "The powers delegated by the proposed Constitution to the federal government are few and defined." Nor did he change his mind in his later years, writing that "With respect to the two words "general welfare,' I have always regarded them as qualified by the detail of powers connected with them. To take them in a literal and unlimited sense would be a metamorphosis of the Constitution into a character which there is a host of proofs was not contemplated by its creators."