The source of United States Patent and Copyright Law is the constitution. More specifically, the foundation for U.S. patent and copyright law is Article I, Section 8, Clause 8 of the Constitution which states:
“The Congress shall have the power . . . to promote the progress of science and the useful Arts by securing for limited times to Authors and Inventors the exclusive right to their respective writings and discoveries.”
Overall, patent law promotes innovation by providing an incentive (limited exclusionary right) to an Inventor for providing a full disclosure (35 USC 112 – Written Description, Best Mode, and Enablement) of their invention so that another can practice the invention freely without restriction after the patent expires.