This document discusses social contract theory and why morality is justified according to philosophers like Thomas Hobbes. Hobbes believed that without common moral rules and laws, humanity would exist in a chaotic state of nature where life would be "solitary, poor, brutish and short." Rational self-interested individuals would therefore agree to social contracts establishing morality as a form of social control. Game theory models also show how morality and cooperation can be in individuals' long-term self-interest by resolving conflicts and allowing societies to function in an orderly way. However, there is a paradox between morality and self-interest, as moral acts are not always the most immediately advantageous choice.