Perhaps not logical; yet it is the basis of Christianity. Christianity originated from Judaism which had taught that sacrifice was necessary to remove the stain of sin. The typical sacrifice was a "lamb without blemish." Jesus portrayed himself as the perfect (and ultimate) sacrifice for the sins of the world. Since the shedding of blood was necessary for the remission of sin, and since Jesus, as the Son of God was the only perfect sacrifice, there was no other way. There is a rather macabre element involved, with the entire idea of bloodletting; yet it explains the idea of justification and forgiveness in terms which the early Christians, who were all Jewish, would understand. To a more modern scholar, it seems somewhat illogical; but one must consider it in the context in which it was originally presented.