Thus, from these facts perhaps we are not reaching an erroneous conclusion [by claiming] that physics, astronomy, medicine, and all the other disciplines which rely upon a consideration of composite objects are indeed doubtful, but that arithmetic, geometry, and the other [sciences] like them, which deal with only the simplest and most general matters and have little concern whether or not they exist in the nature of things, contain something certain and indubitable. For whether I am awake or asleep, two and three always add up to five, a square does not have more than four sides, and it does
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