Marking a major development in Foucault's thinking, Security, Territory, Population derives from the lecture course which he gave at the Collège de France between January and April, 1978. Taking as his starting point the notion of "bio-power," introduced in his 1976 course Society Must be Defended, Foucault sets out to study the foundations of this new technology of power over population. Distinct from punitive, disciplinary systems, the mechanisms of power are here finely entwined with the technologies of security, and it is to 18th century developments of these technologies with which the first chapters of the book are concerned. By the fourth lecture however Foucault's attention turns, focusing on a history of "governmentality" from the first centuries of the Christian era to the emergence of the modern nation state. As Michel Sennelart explains in his afterword, the effect of this change of direction is to "shift the center of gravity of the lectures from the question of biopower to that of government, to such an extent that the former almost entirely eclipses the former." Consequently, in light of Foucault's later work, it is tempting to see these lectures as the moment of a radical turning point at which the transition to the problematic of the "government of self and others" would begin.