The article examines a number of basic concepts of the philosophical discourse of the Russian philosopher of the first half of the twentieth century I. Ilyin. The semantic content and linguistic means of expressing the concepts of GOD, MAN and the WORLD in the book by I. Ilyin «Hegel’s philosophy as a doctrine of the concreteness of God and man» are analyzed. It is concluded that the discursive features of Russian philosophy at the beginning of the twentieth century are fully manifested in the work of the Russian philosopher: a combination of thorough knowledge of Western European philosophical discourse with a high culture of Russian literary speech. It is shown that the concepts like GOD, MAN, the WORLD are the most essential and representative for describing the conceptual field. These concepts express the main ideas of the book, express its theme and idea, which consists in the analysis of Hegel’s philosophy from the point of view of the embodiment of God in the existence of the world and man. The highlighted concepts confirm the presence of the nuclear field in the conceptual field of Ivan Ilyin’s philosophical discourse. The analysis of the text gave grounds to assert that each of the selected concepts has a complex structure of its semantic content, realized through its connections with other concepts in certain syntactic constructions. The attachment of predicates of identification, state, action indicates the definitive signs of the corresponding concepts. The inclusion of verbalizers of nuclear concepts in a subordinate position in syntactic constructions characterizes nuclear concepts from the point of view of their attribution as essential qualities of objects described in the text of Ivan Ilyin – phenomena and facts of nature, society and culture. The article highlights the ontological and mental semantic features of the main concepts, which are revealed in their relations with other concepts. Ontological features are the existence, reality, movement, activity, freedom, spirituality, order, chaos, space, time ascribed to objects expressed by nuclear concepts. Mental signs include various aspects of thinking, knowledge, vision, denial, empirical, sensory, rational knowledge, science.