The permissibility of actions depends upon facts about the flourishing and separateness of persons. Persons differ from other creatures in having the task of discovering for themselves, by conjecture and refutation, what sort of life will fulfil them. Compulsory slavery impermissibly prevents some persons from pursuing this task. However, many people may conjecture that they are natural slaves. Some of these conjectures may turn out to be correct. In consequence, voluntary slavery, in which one person welcomes the duty to fulfil all the commands of another, is permissible. Life-long voluntary slavery contracts are impermissible because of human fallibility; but fixed-term slavery contracts should be legally enforceable. Each person has the temporarily alienable moral right to direct her own life.