Free Thought may be defined as an independent act of the understanding: it corresponds with the French expression, liberté d'esprit. A power of concentrated attention is necessary in processes of reasoning, and forms the foundation of a free and accurate discriminating judgment. The late Dr. Carpenter, in his “Mental Philosophy,” remarks that “in all the leading objects of intellectual occupation, the abstractive power is brought continually into exercise, and hence one advantage of the pursuits of literature, and still more of science.” Copernicus was described by Kepler as a man liber aninto, free in thought, and on account of his unbiassed mind he was regarded as well qualified to undertake the difficult task of preparing an approximately correct diagram of the solar system.