Most of the Bill of Rights is written in the unqualified language of self-evident moral truths or imperative legal statements, but the Second Amendment is framed in terms of a specific instrumental value. Americans value having a free and independent nation, and no such nation can possibly exist without a corps of well-armed citizen volunteers, therefore we must never prevent citizens from acquiring the sort of weaponry which would serve them well on the battlefield, defending their nation from existential threats such as foreign armies.
I’m paraphrasing, of course, but that is essentially what it says. Here, see for yourself:
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.
There is a factual claim being made here, a proposition worth carefully considering. Is it really true that no free state can exist without a well regulated militia? Let us stipulate that “militia” should be taken in the sense given by Webster’s 1828:
The body of soldiers in a state enrolled for discipline, but not engaged in actual service except in emergencies; as distinguished from regular troops, whose sole occupation is war or military service. The militia of a country are the able bodied men organized into companies, regiments and brigades,with officers of all grades, and required by law to attend military exercises on certain days only, but at other times left to pursue their usual occupations.
The question then is whether there are any free nations which have remained secure to this day using only professional soldiers rather than relying on citizen volunteers. This is actually a trickier question than it seems, since the professionalization and incorporation of the militias into the regular armies has been a gradual process across most of the free west, but at this point it wouldn’t be unfair to say that most militiamen and women train with the regular armies and are usually considered legally accountable thereto. In other words, the independent citizen militias have been at least partially incorporated into national standing armies, to train with them and supplement their numbers in times of crisis.
I’m no historian, but it seems obvious that most free nations have been kept secure primarily through the efforts of professional standing armies rather than well-regulated citizen militias. Maybe I’m mistaken, though. If free nations are still calling up citizen soldiers to bring their own rifles and ammunition to the field of battle, I’d be interested in hearing about it. Otherwise, the Second Amendment would appear to be grounded in a proposition that makes as much sense today as the need for a Constitutional prohibition on quartering troops in our homes.