Market interactions are brought about by the interplay of entitlements and obligations. Entitlements are rights, as perceived by the individuals. They are subjectively perceived rights that go along with a motivational disposition to defend them. Obligations are the counterparts of entitlements. They refer to claims of others that are subjectively accepted, and go along with a motivational disposition to respect these claims. Very simple transactions must rely on a system of entitlements and obligations. Simple selfishness would not be sufficient to bring them about or sustain them. This is especially true for nonenforceable contracts. The relationship of entitlements and obligations to norms is also discussed.