Struggling under the weight, the Good Samaritan lifts the limp body of a man—stripped, beaten and left half dead by robbers—onto his horse. In this 1890 painting by Vincent Van Gogh (based on a painting by Eugène Delacroix), the robbers have taken everything but the man’s empty traveling case.

Further along the road, we see the backs of a Levite and a priest—both Jewish religious authorities—as they walk away, having failed to stop and help the man. Only the Samaritan—an adherent of an offshoot of Judaism, traditionally at odds with the Jews—stops to help.

In the Gospel of Luke (10:25–37), Jesus presents the Samaritan …