How did the birth of Jesus change the world? Historian Rodney Stark argues that there was one huge factor that helped capture the attention of the ancient world—Christianity's revolutionary emphasis on mercy. Stark writes:

In the midst of the squalor, misery, illness, and anonymity of ancient cities, Christianity provided an island of mercy and security ….. It started with Jesus ….

In contrast, in the pagan world, and especially among the philosophers, mercy was regarded as a character defect and pity as a pathological emotion: because mercy involves providing unearned help or relief, it is contrary to justice …. [Thus] humans must learn "to curb the impulse [to show mercy]"; "the cry of the undeserving for mercy" must go "unanswered." "[Showing mercy] was a defect of character unworthy of the wise and excusable only in those who have not yet grown up."

This was the moral climate in which Christianity taught that … a merciful God requires humans to be merciful.