I intend to write a few articles about the second amendment over the next few weeks. In this and the following two blog posts, I'll discuss the historical background for the right to keep and bear arms, talk about the legal history of the matter, and then examine the impact of gun control in the United States and abroad on crime and society in general.
Precursor to the Constitution
In the mid 1700's, Parliament passed a number of measures designed to increase tax revenue from the colonies, including the Molasses Act (1733), the Sugar Act (1764), and the Stamp Act (1765). The American colonies had no representatives in Parliament, and no influence over what taxes were levied against them. The colonists were increasingly unwilling to tolerate this taxation without representation, and although the Stamp Act was eventually repealed, Parliament continued to insist [in the Declaratory Act of 1766] that it basically had unquestionable authority over the colonies regardless of their lack of representation in Parliament.
By the mid 1770's, hostilities between the colonies and the British were at a boiling point, and in 1776, the Continental Congress adopted the Declaration of Independence and in doing so resolved to fight to overcome an "unwarrantable jurisdiction" that was "deaf to the voice of justice," in the words of the Declaration, largely written by Thomas Jeffferson. General Thomas Gage was sent to disarm the Patriots in Boston and elsewhere, resulting in the battles of Lexington and Concord. The war was ignited, and from 1775 to 1783, the colonies fought for "Life, Liberty, and the pursuit of Happiness."
The Constitution and the Bill of Rights
The Constitution was adopted by the Constitutional Convention in Philadelphia (ironic, since Philadelphia treads more heavily on liberty than many other places... but that's a story for another day) in 1787 and ratified by conventions in each state. It lays out the 3 branches of the federal government (Legislative, Executive, and Judicial), and established the limits on state and federal governments.
The Bill of Rights is the name given to the first 10 amendments to the Constitution, which were passed collectively in 1791 and which limit the power of the federal government and protect the rights of Americans, including the freedom of religion, freedom of speech, right to keep and bear arms, etc.
The Second Amendment
The Text Itself
First, a refresher course:
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.
What is the Militia?
In Colonial America, the militia was "a group of citizens who would be ready to fight in any emergency," according to Pulitzer Prize-winning author and historian Garry Willis.
"Who are the militia? Are they not ourselves? Is it feared, then, that we shall turn our arms each man gainst his own bosom. Congress have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birthright of an American...[T]he 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.
The whole of that Bill [of Rights] is a declaration of the right of the people at large or considered as individuals...It establishes some rights of the individual as unalienable and which consequently, no majority has a right to deprive them of.
- Albert Gallatin of the New York Historical Society, in a letter to Alexander Addison in 1789
This is subject to some debate, but I hold that the Second Amendment protects the rights of all individuals, not some formally trained military organization. This particular component of the Bill of Rights was influenced heavily by the English Bill of Rights of 1689, which among other things, protected protestants against disarmament by the Crown.
I will explain the legal background for this viewpoint in my next post.
Why did the founding fathers want us to be armed?
The founding fathers, by and large, recognized that, in addition to the need for self-defense against violent crime, an armed populace is a final safeguard against tyranny. When numerous attempts at a peaceable resolution of their grievances with Parliament failed, they resisted with force and won their freedom. They wanted us to have the same ability to resist tyranny. The same reasons - self defense, and as a safeguard against tyranny, have been upheld by the supreme court as a justification for the right to keep and bear arms, in DC vs. Heller, where Justics Scalia said "the right of the people to keep and bear Arms, shall not be infringed" was a just a controlling one and referred to it as a pre-existing right of individuals to possess and carry personal weapons for self defense and intrinsically for defense against tyranny." 
Some more relevant quotes from the founding fathers:
"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 inevitably ruined."
- Patrick Henry 
"Before a standing army can rule the people must be disarmed; as they are in almost every kingdom 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 that can be, on any pretence, raised in the United States."
- Noah Webster 
"God grants liberty only to those who love it, and are always ready to guard and defend it."
-Patrick Henry 
"They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety."
- Benjamin Franklin 
"To preserve liberty, it is essential that the whole body of the people always possess arms, and be taught alike, especially when young, how to use them."
- Richard Henry Lee, whose famous resolution of June 1776 led to the United States Declaration of Independence, for which he was a signer. 
"Laws that forbid the carrying of arms...disarm only those who are neither inclined nor determined to commit crimes. Such laws make things worse for the assaulted and better for the assailants; they serve rather to encourage than prevent homicides, for an unarmed man may be attacked with greater confidence than an armed one"
- Thomas Jefferson, quoting Cesare Beccaria's Essay on Crimes and Punishments 
Militia vs. Individual Ownership
"The best we can hope for concerning the people at large is that they be properly armed."
- Alexander Hamilton 
"No free man shall ever be debarred the use of arms."
- Thomas Jefferson, Proposed Virginia Constitution 
"I ask, sir, what is the militia? It is the whole people, except for a few public officials."
-George Mason 
Some time in the next week or so I will talk about the legal history of the 2nd amendment, and it's protection of the individual's right to keep and bear arms.
 Speech of Patrick Henry Before the Virginia Ratifying Convention, June 5, 1788 (Google Book)
 Noah Webster's Federalist Paper No. 46 (Google Book)
 Speech by Noah Webster addressing the Senate in regards to the Memorial of the Pennsylvania State Convention (Google Book)
 Diplomatic correspondence from Benjamin Franklin (Google Book)
 (Google Book)
 The Federalist Papers at 184-8
 Proposed Virginia Constitution. FORD ED., ii, 27. (June, 1776)
 Debates in Virginia Convention on Ratification of the Constitution, Elliot, Vol. 3, June 16, 1788