George Henry Lewes (1864). “Aristotle: a chapter from the history of science including analyses of Aristotle's scientific writings”, p.9, London : Smith, Elder and Company
George Henry Lewes (1874). “Problems of Life and Mind: The method of science and its application to metaphysics. The rules of philosophising. Psychological principles. The limitations of knowledge”, p.2
George Henry Lewes (1874). “Problems of Life and Mind: The method of science and its application to metaphysics. The rules of philosophising. Psychological principles. The limitations of knowledge”, p.17