Reading Elliot Johnson's Expository Hermeneutics reminded me of of an old truth (as if there is any other kind) by means of a particularly clear statement.
In [Paul's] later affirmation "not all who are descended from Israel are Israel (Rom. 9:6), Paul emphasizes that "physical is not sufficient"—which is quite different from saying "physical is not necessary or essential" (p. 48).
Too many people are saying the latter. We should be affirming the former.