Core Spiritual Science comprises Rudolf Steiner's foundational systematic works, in which he articulates the structure of the human being, the nature of higher worlds, the methods by which those worlds may be investigated, and the evolutionary history of humanity and the cosmos. These texts form the theoretical and practical backbone of Anthroposophy as a discipline. Central volumes include GA 9 (Theosophy), GA 10 (Knowledge of the Higher Worlds), and GA 13 (Occult Science – An Outline), each of which approaches the subject from a distinct angle: the constitution of the human being, the path of inner development, and the broad sweep of cosmic and earthly evolution respectively. Together they establish the vocabulary — etheric body, astral body, ego, Imagination, Inspiration, Intuition, Akasha Chronicle — that recurs throughout Steiner's entire output.