MacDonald develops a theory of anti-Semitism based on an evolutionary interpretation of social identity theory. Historical examples of anti-Semitism are analyzed as scientifically comprehensible gentile responses to a distinctive, segregated group. Anti-Semitism has historically been exacerbated by resource competition between Jews and gentiles. Jews have engaged in a wide range of strategies to try to combat it. These strategies include: crypsis, political activity, writing religious and intellectual apologia directed at both ingroup and outgroup members, and engaging in self-deception regarding both the nature of Judaism and gentile responses to Judaism.