This chapter explores Pascal’s skeptical outlook, highlighting his innovations as well as his reliance on older, more familiar arguments. To begin with, Pascal thought that reason itself could not provide the foundations or first principles of geometry or our knowledge of space. These first principles are not only unsupportable by any proof, so that reason itself provides them no certainty, but they in turn provide materials for further uncertainty given potential infinities in space – both the largeness and smallness of space seems to have no bounds. The result is that we cannot, by appeal to reason alone, find our place within the physical universe. Similarly, and contra Descartes, no proof of God can guarantee that life is not one long dream, so belief in the external world itself cannot be supported by reason. Nor can our experience of the world prove the existence of God in any useful way. The result is that our reason and experience, operating on their own, are insufficient to establish much of anything foundational. The appeal to proofs and evidence cannot resolve other controversies of our day, either, as anyone who has tried to convince a conspiracy theorist by such methods will know.