 By connecting mathematical certainty to the approbation of others Hume gives an essentially social character to mathematical knowledge. No matter the different metaphysical and epistemic pedigree of its branches, it is their practices that determine the certainty of mathematical conclusions (THN 2.3.10.2). In practice geometrical reasoning is elevated to the same level of certainty as our reasoning in arithmetic and algebra—and his may be one way to explain why the Enquiry (EHU 4.1, 7.1–2, 12.20) lists all of them as demonstrative. The limitations of our practices, arising from human nature, condemn all branches of mathematics to eventual fallibility and uncertainty. But that is not the main lesson we should draw here. What really matters is that despite this fallibility we generate certainty through our predominantly social practices. So geometry in practice can be as certain and demonstrative as arithmetic is in principle demonstrative, but in practice, fallible. Taken together, the metaphysics and practice of mathematics leads us to pretty much the same epistemic grounds in all branches of mathematics.