Fact-Sensitivity of the Constitutional Referent
Apropos of Mike Ramsey's post below and Will Baude's request that I call my office, I think I want to take Mike Dorf's side here. It is possible for everyone at the time of the Founding to agree about a constitutional outcome, but nonetheless to be wrong. Everyone at the time the Constitution was drafted (at least, everyone who mattered when the interim rules of Art. I, sec. 2, cl. 3 were drafted) thought that it was constitutional to give more representatives to Maryland than to North Carolina. But that conclusion depended on the incorrect-but-apparently-universal belief among the relevant Founders that Maryland's free-population-plus-three-fifths-of-its-enslaved-population was larger than North Carolina's (see here at 1623). The constitutional rule is "according to their respective numbers," and that applies to the actual facts, even if all of the relevant Framers got those facts wrong. Similarly, as Mike Dorf explains, if "bear" in the context of the Second Amendment means "bear in the home or in public, subject to governmental restrictions as to manner," then it might be permissible to regulate the manner of public arms-bearing (e.g., by requiring open carrying), even if it would not be permissible to ban public arms-bearing altogether. Whether concealed-carry bans are constitutional might depend on whether they are paired with open-carry bans. If they were not paired with open-carry bans at the Founding, then the Founders' partly-fact-dependent conclusion would not be binding on us today, because it was not actually baked into the Constitution itself.
"Semantic originalism" is a term which I think Ronald Dworkin invented in his reply to Scalia's Tanner Lectures to make a point which I think works better if put in terms with a longer philosophical pedigree. I use "original textually-expressed sense," building on a tradition in the philosophy of language going back to Gottlob Frege (and beyond; a very influential seventeenth century logic textbook by Arnauld and his colleagues made the same distinction) to make the same point (at least, a point which I think is the same as Dworkin's!). It's not absolutely clear quite what Dworkin meant by the term, but he distinguished between "semantic originalism" and "original expectations originalism"; I take Dorf's "First Order Originalism" to be likewise anchored solely in original expectations (Fregean referent, Carnapian extension, and Millian denotation, as I would put it), rather than higher-order notions like meaning (Fregean sense, Carnapian intension, or Millian connotation, as I would put it).
As I see it, the sense originally expressed by the text of the Constitution is what the phrase "this Constitution" in Article VI makes binding, not the original reference or collection of things referred to by the Constitution. Building cars changes the referent of "car," but not its sense. Banning open carry might likewise change the referent of the category "the right of the people to keep and bear arms," while leaving the binding sense expressed by those words (as originalists rightly insist) unchanged.