Luhmann’s theory has been commonly considered as a radical overcoming of the traditional philosophy. The interpreters often refer to the non-ontological background of the theory as the criticism of the conscience's centrality, the emphasis in conflict and distinction and the influence of sciences as cybernetic, biology and mathematics. In the present paper we try to demonstrate that there is also an important philosophical heritage in the Luhmann’s sociological work: the Hegelian heritage. We refer to four main points: the congruence of being and thought; the being as the unity of unity/distinction; the rationality as auto-reference and the congruence between theory and society. The focus of our analysis is on the complications of the system theory when it tries to eliminate the idea of spirit.