In 1391, the escalating persecution suffered by Iberian Jewry led to mass conversions, which continued as the Jews’ situation worsened. The presence of large populations of former Jews, and the return of some of their descendants to Judaism in subsequent generations, challenged the way both Jews and Gentiles understood Jewish identity. David Graizbord explains how:

By . . . 1415, some half to two-thirds of Castilian and Aragonese Jews had become titular Christians. Irrespective of the sincerity [of their conversions], or lack thereof, in many if not most cases the converts and their immediate, baptized descendants still lived among, or relatively close to, Jews and had extensive social, economic, and familial relations with them. This meant that for the first time, the religion and the ethnicity of tens of thousands of people once known and still widely regarded as “Jews” were at odds: these “New Christians” were “Jewish” as concerned their social and economic relations, their ethnic culture, and their social reputation, yet their religious identity was at least theoretically identical to that of the majority population.

Of particular interest in this connection is the promulgation as early as 1436 of private and municipal statutes of “Purity of Blood.” This concept formally recast and stigmatized Jewishness as a matter of descent rather than of official religious status, much less of demonstrable belief and behavior. Equipped with this new notion of purity, “Old Christians” began to treat questions of morality and religious fealty as matters of familial heredity.

For their part, Jews acquired a correspondingly acute consciousness of their genealogy. . . . Jewish letters of introduction from the late 1300s and early 1400s, [i.e. from when mass conversion began], differ from older ones in explicitly distinguishing between “good” Jewish families—that is to say, families whose members had not converted—and families sullied by Christianization. A fateful message of the letters was that while Iberian Jews may share ethnicity, their differing fealty to God rendered them essentially separate. What now mattered for purposes of determining a Jew’s character as a Jew, was not only the quality of his or her behavior as an observer of mitzvot, but the caliber of his or her yiḥus [lineage].

Yesterday, the Iranian foreign minister flew to Geneva to meet with European diplomats. President Trump, meanwhile, indicated that cease-fire negotiations might soon begin with Iran, which would presumably involve Tehran agreeing to make concessions regarding its nuclear program, while Washington pressures Israel to halt its military activities. According to Israeli media, Iran already began putting out feelers to the U.S. earlier this week. Aviram Bellaishe considers the purpose of these overtures:

The regime’s request to return to negotiations stems from the principle of deception and delay that has guided it for decades. Iran wants to extricate itself from a situation of total destruction of its nuclear facilities. It understands that to save the nuclear program, it must stop at a point that would allow it to return to it in the shortest possible time. So long as the negotiation process leads to halting strikes on its military capabilities and preventing the destruction of the nuclear program, and enables the transfer of enriched uranium to a safe location, it can simultaneously create the two tracks in which it specializes—a false facade of negotiations alongside a hidden nuclear race.