Chief justice john marshall, in the supreme court's opinion from mcculloch v. maryland (1819), in which the court had to decide whether the constitution gave congress the power to create a national bank: "[the] constitution [is] intended to endure for ages to come, and consequently to be adapted to the various crises of human affairs. to have prescribed the means by which government should, in all future time, execute its powers would have been to change entirely the character of the instrument and give it the properties of a legal code. it would have been an unwise attempt to provide by immutable rules for exigencies which, if foreseen at all, must have been seen dimly, and which can be best provided for as they occur."

The decision by the Marshall court was highlighting the "necessary and proper" clause of Article I, Section 8, of the United States Constitution.

After enumerating a number of the powers of Congress, including borrowing money, coining money, regulating commerce, etc, Section 8 of Article I closes with by saying Congress shall have 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 in any Department or Officer thereof."  

The statement of the Marshall court in regard to the chartering of a national bank held significance beyond that issue as well.  The ruling said:  "Let the ends be legitimate, let it be within the scope of the Constitution, and all means which are appropriate, which are plainly adopted to that end, which are not prohibited, but consist with the letter and spirit of the Constitution, are constitutional."  The quoted section which you have above also displays this principle that asserts a "loose constructionist" view of the Constitution is embedded in the Constitution's own wording as "necessary and proper."

Athe rate increases as income increases