 The popularity of a mathematical proof (or demonstration) among experts in the field naturally speaks in favor of the proof. This feature is not peculiar to mathematical conclusions, because as Hume points out: “I feel all my opinions loosen and fall of themselves, when unsupported by the approbation of others” (THN 1.4.7.4). What makes mathematics peculiar is that, in addition to individual reasoning, the approbation of the mathematician’s close circle of “friends”, and the approval of the scholarly community seem to be the only sources of justification in matters of mathematics.