This article was prepared on the basis of the manuscript of academician Alexander Sergeyevich Lappo-Danilevsky (1863–1919) “On sociology”, deposited in the fund of the scientist in the St. Petersburg branch of the Russian Academy of Sciences archive (Fond 113). The ideas of A. Lappo-Danilevsky in the neo-Kantian trend in sociology, in particular, the concept of “revival of natural law” of R. Stammler. While appreciating the social and philosophical doctrine of German neo-Kantian A.S. Lappo-Danilevsky criticized R. Stammler for not a complete carrying out “formal principle” in sociology, ignoring the problem of the “other self”, etc. A.S. Lappo-Danilevsky believed that social science should not be based on an external rule, and on the concept of interaction. The article presents the fragments of the manuscript A.S. Lappo-Danilevsky.