The separatist spirit which would erect the pediment of truth on the single pillar of yoga alone or of metaphysics alone ends always in failure or, worse, in disaster. When each sphere of activity whose integral union is needed for the successful completion of the structure asserts its self-sufficiency, it begins to suffer what in the individual human being is called an enlarged ego. The student of metaphysics who despises mysticism and the student of mysticism who despises metaphysics will pay the penalty of neurosis for this unhealthy and unbalanced state of his mental life.
-- Notebooks Category 20: What Is Philosophy? > Chapter 3: Its Requirements > # 392