One of the best-known and most influential present-day treatments of liberty is that of Sir Isaiah Berlin. In his Two Concepts of Liberty, Berlin upheld the concept of “negative liberty” â€” absence of interference with a person’s sphere of action â€” as against “positive liberty,” which refers not to liberty at all but to an individual’s effective power or mastery over himself or his environment.
Superficially Berlin’s concept of negative liberty seems similar to Rothbard’s: that liberty is the absence of physically coercive interference or invasion of an individual’s person and property. Unfortunately, however, the vagueness of Berlin’s concepts led to confusion and to the absence of a systematic and valid libertarian creed. FULL ARTICLE