Explanation: If you want to know what the government can do, specifically, you can look at Article I, Section 8 of the Constitution, which lists Congress' powers: it can levy taxes, declare war, and coin money, among other things. These are called the government's enumerated powers, also called expressed powers or delegated powers.
The immediate problem faced by the framers of the Constitution was that it was impossible to list all the powers of government. First off, there are just too many; and second, they wanted to build a government that would last and stands the test of time. They knew that the world was going to change; remember, these were all very educated and enlightened men, raised in the 18th century, the Age of Reason. They knew they couldn't predict what the world would look like in even ten years, much less in a century.
So, they added a rule. Near the end of Section 8 of the Constitution, it says: 'Congress has the power to make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of the United States, or any Department or Officer thereof.
What does this mean? Two things: first, don't think that the powers listed here are the government's only powers. Second, Congress can make any law it needs to, to carry out its enumerated powers. This 'necessary and proper clause, then, allows the government to stretch beyond its literal description; that's why the clause is often nicknamed the elastic clause since its flexibility allows the government to change and grow over time.
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