ABSTRACTAccording to many contemporary observers, including Hillel Steiner [1], Herbert Hart [2], John Gray [3] and Isaiah Berlin [4], the equal liberty principle lies at the heart of liberalism. Yet despite its central place in liberal theory, it has attracted little critical appraisal. This paper seeks to examine the meaning and some of the policy implications of the equal liberty principle, paying particular attention to the elucidations produced by Herbert Spencer, Steiner and Hart — the only systematic analysts of the notion of equal liberty. In part 1, the meaning of the equal liberty principle is discussed, and it is shown to be intrinsically ambivalent. In part 2, where certain policy implications are considered, the conclusion is reached that the equal liberty principle is ambiguous in its policy prescriptions, and requires to be supplemented by some other principle before it can be unequivocally applie