What Does It Mean to See Paul "within Judaism"?

What happens if we think of "Jewish law" not as a category of Christian theology but as an element of ancient kinship construction, "ancestral custom" (Gal 1:14)? We will see more clearly how much late Second Temple Judaism shared with contemporary Mediterranean cultures. We will see how ancient ethnic essentialism—the conviction that different peoples evinced different behaviors because of their very "nature" (φύσις)—shapes Paul's thought about gentiles no less than it shaped Greek thought about Persians, or Roman thought about Greeks. We will see how Jewish law provided not the contrast to Paul's gospel but in fact much of its content. We will see that there is no reason to assume that Paul stopped living Jewishly (Ἰουδαϊκῶς) just because he wanted gentiles to stop living "paganly" (ἐθνικῶς). We will let Paul reside coherently in a world radically different from our own—the ethnically essentialist, behaviorally variegated, god-congested world of first-century Jewishness.