As Thomas Jefferson said (full quote below) "rulers are not warned from time to time." To effectively warn someone and to be able to give effective resistance one must be effectively armed.
Before a standing army can rule, the people must be disarmed, as they are in almost every country in Europe. The supreme power in America cannot enforce unjust laws by the sword; because the whole body of the people are armed, and constitute a force superior to any band of regular troops."
- Noah Webster, An Examination of the Leading Principles of the Federal Constitution, October 10, 1787
"What country can preserve its liberties if their rulers are not warned from time to time that their people preserve the spirit of resistance. Let them take arms."
- Thomas Jefferson, letter to James Madison, December 20, 1787
"The right of the citizens to keep and bear arms has justly been considered, as the palladium of the liberties of a republic; since it offers a strong moral check against the usurpation and arbitrary power of rulers; and will generally, even if these are successful in the first instance, enable the people to resist and triumph over them.”
– Joseph Story, Commentaries on the Constitution of the United States, 1833
"Guard with jealous attention the public liberty. Suspect everyone who approaches that jewel. Unfortunately, nothing will preserve it but downright force. Whenever you give up that force, you are ruined…. The great object is that every man be armed. Everyone who is able might have a gun.”
– Patrick Henry, Speech to the Virginia Ratifying Convention, June 5, 1778
Are we at last brought to such humiliating and debasing degradation that we cannot be trusted with arms for our defense? Where is the difference between having our arms in possession and under our direction, and having them under the management of Congress? If our defense be the real object of having those arms, in whose hands can they be trusted with more propriety, or equal safety to us, as in our own hands?”
-Patrick Henry, Debates in the Several State Conventions on the Adoption of the Federal Constitution
“f circumstances should at any time oblige the government to form an army of any magnitude that army can never be formidable to the liberties of the people while there is a large body of citizens, little, if at all, inferior to them in discipline and the use of arms, who stand ready to defend their own rights and those of their fellow-citizens. This appears to me the only substitute that can be devised for a standing army, and the best possible security against it, if it should exist.”
– Alexander Hamilton, Federalist No. 28, January 10, 1788
And that the said Constitution be never construed to authorize Congress to infringe the just liberty of the press, or the rights of conscience; or to prevent the people of the United States, who are peaceable citizens, from keeping their own arms; or to raise standing armies, unless necessary for the defense of the United States, or of some one or more of them; or to prevent the people from petitioning, in a peaceable and orderly manner, the federal legislature, for a redress of grievances; or to subject the people to unreasonable searches and seizures of their persons, papers or possessions.”
– Samuel Adams, Massachusetts Ratifying Convention, 1788
“As civil rulers, not having their duty to the people before them, may attempt to tyrannize, and as the military forces which must be occasionally raised to defend our country, might pervert their power to the injury of their fellow citizens, the people are confirmed by the article in their right to keep and bear their private arms.”
– Tench Coxe, Philadelphia Federal Gazette, June 18, 1789
“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
“(C)onceived it to be the privilege of every citizen, and one of his most essential rights, to bear arms, and to resist every attack upon his liberty or property, by whomsoever made. The particular States, like private citizens, have a right to be armed, and to defend by force of arms, their rights, when invaded.”
-Roger Sherman, Debates on 1790 Militia Act
I prefer dangerous freedom over peaceful slavery.”
– Thomas Jefferson, letter to James Madison, January 30, 1787
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.”
– Benjamin Franklin, Historical Review of Pennsylvania, 1759