Document 6, House of Representatives, Amendments to the Constitution, 17, 20 Aug. 1789Annals 1:749–52, 766–67 http://press-pubs.uchicago.edu/founders/documents/amendIIs6.html

"A well regulated militia, composed of the body of the people, being the best security of a free state, the right of the people to keep and bear arms shall not be infringed; but no person religiously scrupulous shall be compelled to bear arms."

Mr. Gerry.--This declaration of rights, I take it, is intended to secure the people against the mal-administration of the Government; if we could suppose that, in all cases, the rights of the people would be attended to, the occasion for guards of this kind would be removed. Now, I am apprehensive, sir, that this clause would give an opportunity to the people in power to destroy the constitution itself. They can declare who are those religiously scrupulous, and prevent them from bearing arms.

....

Whenever Governments mean to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise an army upon their ruins.... This was actually done by Great Britain at the commencement of the late revolution. They used every means in their power to prevent the establishment of an effective militia to the eastward.

The constructors were so intent on not violating peoples’ rights that the amendment originally had “but no person religiously scrupulous shall be compelled to bear arms”, but, Gerry, being rightfully paranoid about governments’ misuse, reinterpretation, and misconstruction of law thought that phrase provided the opportunity for government to “invade the rights and liberties of the people”.  Gerry said: “Whenever Governments mean to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to []raise an army[] upon their ruins”. And, what better way to destroy the militia than to, as he put it, declare all people religiously disposed not to bear arms and then deprive them of that right, and thus make them incapable of forming a militia.

let’s continue from the source:


Mr. Jackson was willing to accommodate. He thought the expression was, "No one, religiously scrupulous of bearing arms, shall be compelled to render military service, in person, upon paying an equivalent."
Mr. Stone inquired what the words "religiously scrupulous" had reference to: was it of bearing arms? If it was, it ought so to be expressed.

Stone makes it clear there are at least two things being considered – “bearing arms” and something else, presumably “serving in a militia” – making it, once again, clear the two things are different.