In a “vertical” argument discussed in Robert Fogelin’s book on this thinker’s “crisis,” this thinker suggested that a mathematician checking their work will face an infinite regress of decreasing credences in their judgements. A statement named for this thinker faces the Bad Company problem, since its use of (-5[1])equinumerosity can be swapped out to create more dubious abstraction principles. This thinker suggested that books containing neither “abstract reasoning concerning quantity or number” nor “experimental reasoning” could be committed to flames, (10[2])since they contain (10[1])“nothing but sophistry and illusion.” A “principle” that neo-Fregeans (10[1])(“neo-FRAY-ghee-uns”) use to define numbers is named for this thinker, who grouped mathematical truths as “relations of ideas,” (10[1])not (10[2])“matters (10[1])of fact.” (10[5])For (10[1])10 points, name this author (10[1])of An Enquiry (10[1])Concerning (10[1])Human (10[1])Understanding. (10[1]-5[1])■END■ (10[2])