 Since these justifications of property do not rest on a prior principle of self-ownership, they are not committed to seeing property rights as in any way absolute, immune to just regulation, or even precluding any and all forms of taxation. Despite what is sometimes suggested (Freeman 2001), virtually all libertarians that reject self-ownership as a starting point also accept that property rights need specification, can be instantiated in quite different, yet morally acceptable forms, and might be overridden by other moral considerations. Such views do not entail the impossibility of unilateral original appropriation either.