Berlin contended that under the influence of Jean-Jacques Rousseau, Immanuel Kant and G. W. F. Hegel (all committed to the positive concept of liberty), European political thinkers often equated liberty with forms of political discipline or constraint. This became politically dangerous when notions of positive liberty were, in the nineteenth century, used to defend nationalism, self-determination and the Communist idea of collective rational control over human destiny. Berlin argued that, following this line of thought, demands for freedom paradoxically become demands for forms of collective control and discipline – those deemed necessary for the "self-mastery" or self-determination of nations, classes, democratic communities, and even humanity as a whole. There is thus an elective affinity, for Berlin, between positive liberty and political totalitarianism.
Conversely, negative liberty represents a different, perhaps safer, understanding of the concept of liberty. Its proponents (such as Jeremy Bentham and John Stuart Mill) 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 the philosophical harbingers of modern totalitarianism. It is this concept of Negative Liberty that Isaiah Berlin was a proponent of. It dominated heavily his early chapters in his third lecture.
This negative liberty is central to the claim for toleration due to incommensurability. This concept is mirrored in the work of Joseph Raz.
The third and last part of Adam Curtis's documentary series The Trap discusses Isaiah Berlin's concepts of positive and negative liberty, especially in the context of the Iraq War and the War in Afghanistan (2001–present) as a result of the global War on Terror. Curtis argues that even the idea of negative freedom had become dangerous in that Western governments especially the United States of America and the United Kingdom are justifying violence, social and economic breakdown and political tyranny to impose negative freedom on other countries as well as their own people. He suggests that the quest for positive freedom may not necessarily lead to violence and tyranny and that a return to the constructive ideals of positive freedom may be imperative....Continua