So that when a thing is said to appear great or small, or whatever
estimate be made of the magnitude of any thing, this is meant not of the
visible but of the tangible object. This duly considered, it will be no
hard matter to reconcile the seeming contradiction there is, that the
moon should appear of a different bigness, the visible magnitude thereof
remaining still the same. For by sect. 56 the very same visible
extension, with a different faintness, shall suggest a different tangible
extension. When therefore the horizontal moon is said to appear greater
than the meridional moon, this must be understood not of a greater
visible extension, but a of greater tangible or real extension, which by
reason of the more than ordinary faintness of the visible appearance, is
suggested to the mind along with it.
75. Many attempts have been made by learned men to account for this
appearance. Gassendus, Descartes, Hobbes, and several others have
employed their thoughts on that subject; but how fruitless and
unsatisfactory their endeavours have been is sufficiently shown in THE
TRANSACTIONS,[Phil. Trans. Num. 187. p. 314] where you may
see their several opinions at large set forth and confuted, not without
some surprize at the gross blunders that ingenious men have been forced
into by endeavouring to reconcile this appearance with the ordinary
Principles of optics.
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