premise: That's right. That's the important hurdle, and we'd like to jump that first, but the other ones, Justice, you're right, in 1831 and in 1909 Congress extended terms in a way that is inconsistent with the strongest form of the test that we have advanced. Those extensions, however, were never challenged in any court and certainly not considered by this Court.
hypothesis: In 1909 Congress made  a bad decision to extend terms.
reason: I have no idea why congress extended terms- it could have been bad or could not. 