 The central insight of foundationalism is to organize knowledge in the manner of a well-structured, architectural edifice. Such an edifice owes its structural integrity to two kinds of features: a firm foundation and a superstructure of support beams firmly anchored to the foundation. A system of justified beliefs might be organized by two analogous features: a foundation of unshakable first principles, and a superstructure of further propositions anchored to the foundation via unshakable inference.