Mathematics is, I believe, the chief source of the belief in eternal and exact truth, as well as in a super-sensible world. Geometry deals with exact circles, but no sensible object is exactly circular; however carefully we use our compasses, there will be some imperfections and irregularities. This suggests the view that all exact reasoning applies to ideal as opposed to sensible objects; it is natural to go further, and to argue that thought is nobler than sense, and the objects of thought more real than that of sense-perception.p. 37.

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