"Two Concepts of Liberty" was the inaugural lecture delivered by the liberal philosopher Isaiah Berlin before the University of Oxford on 31 October 1958.
He also defined it as a comparatively recent political ideal, which re-emerged in the late 17th century, after its slow and inarticulate birth in the ancient doctrines of Antiphon the Sophist, the Cyrenaic discipleship, and of Otanes after the death of pseudo-Smerdis.
He defined positive liberty both as "freedom to", that is, the ability (not just the opportunity) to pursue and achieve willed goals; and also as autonomy or self-rule, as opposed to dependence on others.
Its later proponents (such as Tocqueville, Constant, Montesquieu, John Locke, David Hume and John Stuart Mill,[citation needed] who accepted Chrysippus' understanding of self-determination)[7] insisted that constraint and discipline were the antithesis of liberty and so were (and are) less prone to confusing liberty and constraint in the manner of rationalists and the philosophical harbingers of totalitarianism.
There is thus an elective affinity, for Berlin, between positive liberty, when it is rhetorically conflated with goals imposed from the third-person that the individual is told they "should" rationally desire, and the justifications for political totalitarianism, which contrary to value-pluralism, presupposed that values exist in Pythagorean harmony.
[citation needed] Berlin did not argue that the concept of positive liberty should be rejected—on the contrary, he recognised it as one human value among many, and one necessary to any free society.
[12] Berlin argued, rather, that these differing concepts showed the plurality and incompatibility of human values, and the need to analytically distinguish and trade off between, rather than conflate, them.
Faced with this two-step process, it seems safer and easier to stop it at the first step, to insist firmly that freedom is just a matter of the absence of external obstacles, that it, therefore, involves no discrimination of motivation and permits in principle no second-guessing of the subject by anyone else.