…in light of the enormous social costs of being a Christian in the first three centuries, why did anyone become a Christian? Why did Christianity grow so exponentially? What did Christianity offer that was so much greater than the costs? Hurtado and others have pointed out three things.
First, Christians were called into a unique “social project” that both offended and attracted people. Christians forbade both abortion and the practice of “infant exposure,” in which unwanted infants were simply thrown out. Christians were a sexual counter-culture in that they abstained from any sex outside of heterosexual marriage. This was in the midst of a culture that thought that, especially for married men, sex with prostitutes, slaves, and children was perfectly fine.
Also, Christians were unusually generous with their money, particularly to the poor and needy, and not just to their own family and racial group. Another striking difference was that Christian communities were multi-ethnic, since their common identity in Christ was more fundamental than their racial identities, and therefore created a multi-ethnic diversity, which was unprecedented for a religion. Finally, Christians believed in non-retaliation, forgiving their enemies, even those who were killing them.
Second, Christianity offered a direct, personal, love relationship with the Creator God.