Hume held that we have no rational justification for our inductive beliefs. A more radical view is that we have no rational justification for any of our beliefs. This dissertation has two goals pertaining to this more radical view. // The first goal is to find a basis for constructive epistemology that is consistent with this view. This goal is first sought by considering externalist theories of knowledge since these do not require rational justification for knowledge. Externalist theories are defended (...) against the usual objections, partly via a strategy of immunizing them from counterexample-based objections by arguing that epistemologies can be successful even if they fail to explicate ordinary epistemic notions. But a new objection to externalist theories is then brought to light. The objection begins as an attack against a dogma of contemporary epistemology, that the chief benefit of possessing knowledge is having a true belief. It is argued that there are many other benefits to having knowledge , and that externalist theories are defective because externalist knowledge lacks these benefits. A mixed internalist/externalist theory, bilevel reliabilism, is then presented as a solution to this difficulty. //The second goal is to provide an explanation of the function and origin of human epistemic practices that is consistent with the no-rational-justification view. Providing such an explanation is problematic for holders of this view because, if it is correct, it seems, prima facie, that there is no reason to have epistemic practices. This goal is achieved by arguing that epistemic practices, despite appearing to have rational justification as their goal, chiefly function to promote the existence of bilevel reliabilist knowledge, a very useful type of belief that is not rationally justified. It is then argued that the explanation of the origin of epistemic practices is that they arise from natural human inductive tendencies. (shrink)