The objective of the present article is rating some of the contributions made by Niklas Luhmann's systems theory to the social sciences and philosophy. For this purpose in the introduction becomes a review of systems thinking, complex thought, the concept of totality, systemic explanations. In development are based on the theory of conflict of Luhmann, analyzed: the concept of affected, systemic differentiation, systems and creation of complexity. The analysis of a social movement is also performed in Mexico, to see the achievements, contributions and limits of systems theory. It is concluded that Luhmann is a conservative thinker, ahistorical and that has left aside completely to the subject, which obviously for social sciences brings large theoretical and management risks great practical risks. [ABSTRACT FROM AUTHOR]