This essay is an attempt to defend a liberal position with respect to pornography and prostitution. It against both conservatives and libertarians. It main claims are that to respect freedom of speech, the state may regulate pornography, but should not prohibit pornography, and that in order to provide equal protection of sexual autonomy for all, the state may ban prostitution. Its main arguments are based on a liberal principle of legitimacy, which consists of two parts: (1) the state should ensure the favorable conditions for its citizens to develop and exercise their capacity for a conception of the good; and (2) the state should be neutral with respect to controversial conceptions of the good when it exercises its powers.