Hy did Alexander Hamilton believe that the national bank was constitutional? He believed in express powers and a strict interpretation of the Constitution.
The Constitution states that a government should have all the powers to carry out its duties, and the national bank was necessary.
He thought the Constitution was a weak document that couldn’t address the needs of the government. The Constitution mentioned the possible need for a bank.

a) he believed in express powers and a strict interpretation of the constitution

Explanation:

social contract theory basically says that all individuals are born equal, and provided a god given right to consent to be governed. american government is based of this

thomas hobbes and john locke said that we are selfish, individualistic, and constantly at war with each other, therefore we need to be controlled. 

government is defined as the legitimate use of force to control human behavior within territorial boundaries, here comes in hobbes and locke.

hobbes takes the part about controlling human behavior. while locke takes the part of legitimate use of force, since force is not legitimate unless there is consent of the people. 

there are basically 3 goals of the government: 1) maintain order by protecting life and property. 2) providing public goods, those which are typically not provided by the public sector, such as roads and education. 3) promote equality be it political, opportunist or outcome equality.