Here is a succinct statement on the purpose of the 2nd amendment:
"The militia of these free commonwealths, entitled and accustomed to their arms, when compared with any possible army, must be tremendous and irresistible. Who are the militia? Are they not ourselves? Is it feared, then, that we shall turn our arms each man against his own bosom. Congress have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birth-right of an American ... the unlimited power of the sword is not in the hands of either the federal or state governments, but, where I trust in God it will ever remain, in the hands of the people."
-Tenche Coxe, The Pennsylvania Gazette, Feb. 20, 1788
Tenche Coxe was a political economist a delegate for Pennsylvania to the Continental Congress 1788 - 1789.