That’s what we saw in Paris last week.

Sacks correctly argues that we need military weapons to win the war against fanatics like ISIS, but we need ideas to establish a lasting peace. Secular thought or moral relativism are unlikely to offer any effective rebuttal. Among religious people, mental shifts will be found by reinterpreting the holy texts themselves. There has to be a Theology of the Other: a complex biblical understanding of how to see God’s face in strangers. That’s what Sacks sets out to do.

The great religions are based on love, and they satisfy the human need for community. But love is problematic. Love is preferential and particular. Love excludes and can create rivalries. Love of one scripture can make it hard to enter sympathetically into the minds of those who embrace another.

The Bible is filled with sibling rivalries: Ishmael and Isaac, Esau and Jacob, Joseph and his brothers. The Bible crystallizes the truth that people sometimes find themselves competing for parental love and even competing for God’s love.

Read simplistically, the Bible’s sibling rivalries seem merely like stories of victory or defeat — Isaac over Ishmael. But all three Abrahamic religions have sophisticated, multilayered interpretive traditions that undercut fundamentalist readings.

Alongside the ethic of love there is a command to embrace an ethic of justice. Love is particular, but justice is universal. Love is passionate, justice is dispassionate.

Justice demands respect of the other. It plays on the collective memory of people who are in covenantal communities: Your people, too, were once vulnerable strangers in a strange land.

The command is not just to be empathetic toward strangers, which is fragile. The command is to pursue sanctification, which involves struggle and sometimes conquering your selfish instincts. Moreover, God frequently appears where he is least expected — in the voice of the stranger — reminding us that God transcends the particulars of our attachments.