In recent years Western countries have seen a proliferation of antisemitic material in social media, and attacks on Jews such as that on the Tree of Life synagogue in Pittsburgh in 2018. Much of this has stemmed, not from personal hostility to Jews on the part of this or that individual, but from a resurgence in groups at both ends of politics of the ancient delusion that "the Jews" collectively dominate world affairs and lie at the root of all...