Many libertarians ground their theory of justice in a non-aggression principle. The NAP is often the basis for the libertarian condemnation of state action – that it is necessarily aggressive and therefore unjust. This approach is often criticised insofar as it defines aggression, in part, as the violation of legitimate property rights, and is therefore parasitical upon a prior – and unjustified – theory of property. While it is true that libertarians who defend the NAP sometimes fail to give a (...) satisfactory account of its relationship to libertarian property rights, such an account is in fact available. A commitment to property rights and to non-aggression can both be grounded in a commitment to non-interference. Such a principle, then, brings together the NAP and the theory of property it is parasitical upon, thus saving the unity and austerity of the overall approach. (shrink)