There are two places in the Constitution (as far as I recall) where an assertion is tied to a rationale:
[The Congress shall have power] To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveriesNote that in the former the rationale does limit the scope of the assertion (Congress is not given a power to grant exclusive rights for any old reason, but rather is given a power to advance the arts and sciences using that tool), and that in the latter the rational does not limit the scope of the assertion (the statement that the right shall not be infringed is direct and complete in itself, with the militia clause as a mere reason why it's a good idea).A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.
The courts have got the official interpretation of both of these clauses exactly bass ackwards.