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That sometimes clear ... and sometimes vague stuff ... which is ... mathematics.
In P. Davis and R. Hersh, The Mathematical Experience, Boston: Birkhauser, 1981.
Marin Mersenne's Universal Geometry
The title page of Universal Geometry, by Marin Mersenne (1588 - 1648), published in Paris in 1644. A compendium of material on geometry, mechanics and optics, it considers the theories of Euclid, Archimedes, Ramus, Theodosius, and Apollonius and includes a treatise on optics by the contemporary natural philosopher Thomas Hobbes (1588 - 1679).