The article analyzes the early stage of philosophical and socio-political creativity of Prince Peter A. Vyazemsky during his time in the diplomatic service in Warsaw. It is noted that the young Vyazemsky, being in many respects a typical representative of his social and cultural environment, understood and interpreted the European liberal ideas of the eighteenth and early nineteenth centuries in a deeply understandable and original way with reference to the Russian context. Being not only a thinker, but also a statesman, Vyazemsky made a significant contribution to the development of the constitutionalist tradition in Russian socio-political thought and laid the foundation for the further evolution of his ideas, which in the future drifted from liberalism to moderate conservatism, but with the preservation of that rational and Critical approach, which was inherent in the young Vyazemsky.