Although Luhmann first developed his understanding of social systems theory under Parsons' influence, he soon moved away from the Parsonian concept. The most important difference is that Parsons framed systems as forms of action, in accordance with the AGIL paradigm. Parsons' systems theory treats systems as operationally open, and interactive through an input and output schema. Influenced by second-order cybernetics, Luhmann instead treats systems as autopoietic and operationally closed.Luhmann, N. Social Systems. Stanford University Press, 1995.Luhmann, N. Introduction to Systems Theory. Polity, 2012. Systems must continually construct themselves and their perspective of reality through processing the distinction between system and environment, and self-reproduce themselves as the product of their own elements. Social systems are defined by Luhmann not as action but as recursive communication. Modern society is defined as a world system consisting of the sum total of all communication happening at once,Luhmann, N. Theory of Society, Vol. 1. Stanford University Press, 2012, pp. 83–99. and individual function systems (such as the economy, politics, science, love, art, the media, etc.) are described as social subsystems which have "outdifferentiated" from the social system and achieved their own operational closure and autopoiesis.Luhmann, N. Theory of Society, Vol. 2. Stanford University Press, 2013, pp. 65ff.
Although Luhmann first developed his understanding of social systems theory under Parsons' influence, he soon moved away from the Parsonian concept. The most important difference is that Parsons framed systems as forms of action, in accordance with the AGIL paradigm. Parsons' systems theory treats systems as operationally open, and interactive through an input and output schema. Influenced by second-order cybernetics, Luhmann instead treats systems as autopoietic and operationally closed.Luhmann, N. Social Systems. Stanford University Press, 1995.Luhmann, N. Introduction to Systems Theory. Polity, 2012. Systems must continually construct themselves and their perspective of reality through processing the distinction between system and environment, and self-reproduce themselves as the product of their own elements. Social systems are defined by Luhmann not as action but as recursive communication. Modern society is defined as a world system consisting of the sum total of all communication happening at once,Luhmann, N. Theory of Society, Vol. 1. Stanford University Press, 2012, pp. 83–99. and individual function systems (such as the economy, politics, science, love, art, the media, etc.) are described as social subsystems which have "outdifferentiated" from the social system and achieved their own operational closure and autopoiesis.Luhmann, N. Theory of Society, Vol. 2. Stanford University Press, 2013, pp. 65ff.