In the book of Philemon, what deeper theological principle is Paul illustrating through his appeal on behalf of Onesimus, Philemon's runaway slave?

A That slavery is morally acceptable as long as masters treat their slaves kindly. B That believers should always obey the laws of the land, even if those laws are unjust. C That reconciliation and forgiveness are central to the Christian faith, transcending social barriers and legal obligations. D That Paul was primarily concerned with maintaining social order and avoiding conflict with Roman authorities.