Joe Carter critiquing Andrew Sullivan is already well-trodden ground, so I’ll try to be freshly relevant:

The word ‘Constitution’ in the Oath of Office refers to a specific written document, which we know as the ‘Constitution of the United States.’  (I don’t mean that to sound as condescending as it does; diction requires it.)  ‘Politeia’ is the Greek for ‘constitution’, ‘state’, ‘government-of-the-state’, ‘body-of-laws’, ‘citizen-body’, etc.  It is a vague, ambiguous term, which is why, when you read Aristotle’s Athenaion Politeia, you have to be aware of the nuance within it.  Sometimes he is referring to body of law as aspect of politeia; sometimes to citizen body; sometimes to a far more esoteric term.  From a response paper last quarter:

“The politeia, for Aristotle, was distinct from the state. If, as he says, a state is “an association of citizens in a constitution” (Politics 3.iii, p. 176) then it is in part an the manner in which the state and authority in it are arranged. He goes on to say quite clearly that, “the citizen body is the constitution.” And he later refers to the Four Hundred as “trying to keep control of the constitution” (Politics 5.iv, p. 309): a politeia is an arrangement which can be controlled, and which lends power to those who hold it.

“This supports the view which is implicitly presented in AP that a change in constitution is dependent upon a change in who has control of the state, or a share in running it. At each constitutional change, the number of those who take part in the public life of the state either rises or falls. Solon expands political authority to a wider number of people, and so Pisistratus, even though he behaved “more like a citizen than a tyrant” (AP 16.1, p. 58), caused a constitutional change when he took power because “he would take care of all public affairs” (AP 15.5, p. 57). The aim of Kleisthenes’ reforms of the demes and tribes was to make it “so that more men should have a share in the running of the state” (AP 21.1, p. 63). The rise of the Areopagus is a change because it takes more control of public life, even if it left private affairs alone. Those who had a share in the state shrank, and when it was overthrown, it expanded again.”

If you’re still with me, the point is that, were we working with the Aristotelian concept of the word we roughly (for lack of anything better) translate as ‘constitution,’ Joe Carter would have a much stronger point.  Rather, in American politics and government, there is no ambiguity; ‘Constitution’ (note capitalization) refers specifically to a written document.  The Aristotelian conception is closer to (but still distant from) the model of the British Constitution.

Most notable is the American conceit that the Constitution is the state, directly contrary to the Aristotelian notion of separateness, or what might find in a more ambiguously defined use of ‘constitution.’  If, somehow, all of the current 50 states were lost and Americans forced into exile on previously un (or sparsely) inhabited islands, but kept the Constitution, the state (as well as both constitution and Constitution) would be continuous.

Now, of course protecting/defending the territory is essential to the survival of the state; no state can exist without a land or a people, and cannot long exist purely as an idea.  But preserving/defending the Constitution are also essential.  And because territory is potentially transitory, it can be defending extra-constitutionally, and only the Constitution grants authority, the Oath makes the point of saying it is most essential to the survival of the state: that the state itself is embodied in it.

UPDATE: It would behoove me to note that the Ath Pol was lost until the late 19th century, so, from a Foundational perspective, the Founders could not have been thinking of any portion that was not quoted elsewhere.  However, as can be seen above, the specificity of ‘Constitution’ to a document and the American conception of what it embodies are also contrary to the definition given in his Politics, which was not lost.  The Ath Pol merely serves as an example to better illustrate the matter.

Also, it would further behoove me to disclose that I don’t even think the Ath Pol was written by Aristotle himself but by two distinct students of his (at the same time, more or less, mind you, and on a joint assignment, and possibly edited/proofread by the man  himself).  As far as it pertains to this matter, as students of his and members of his school writing a text that was to be published by it, would be operating with his definition of politeia.  But this matter of authorship, I should note, puts me in a very small minority that runs afoul of the leading scholar of the text… in other words, makes me an eccentric.  (This despite being right.)