I think I get what xeno is saying now.
Every protection guaranteed under the Constitution, whether it be freedom of the press, double jeopardy, or freedom of religion, has one thing in common: their purpose is to check against the government. Freedom of speech was made so that we could protest and voice our opinion about government. The right to a fair trial ensured that the government didn't jail protesters excessively.
Thus, it's reasonable to assume that all constitutional protections were created as a method to create checks against the government.
So then what about the right to bear arms? As cited here, it has three functions:
Hunting
Protecting your home against intruders
Rebellion
So which of these would Jefferson want to protect? Certainly, nobody's saying that Jefferson didn't like hunting. However, you can like many things, yet think they're not worthy of being written in the Constitution: I like Civilization 3, but that doesn't mean I think a constitutional amendment should be written to protect my right to play the game. Look around the Constitution and ask if there are other sports that were constitutionally protected just because they're fun. Any? Is there a soccer amendment?
The way to figure out the "primary justification" for the 2nd amendment, then, is to imagine a modified weapon. Pretend that we live in a world where the gun has only one of the above uses. Would Jefferson have written a constitutional amendment to protect our freedom to hunt? Hunting's nice, but is it really on par with the other amendments?
How about the right to protect your home against intruders? Now this is debatable. I'll leave that between you guys, and I would love to see Flint's reaction. However, it seems like "the right to protect your home against intruders" would, under the Constitution, fall as more of a state's rights issue, as written. But that's just me.
But what about if the only purpose for the gun was open rebellion against the government? Would that be constitutionally protected? It seems to fit into the formula that all amendments are there to create checks against the government. This seems, then, to be the most logical of the three.
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