Hence, generally, a foundationalist might offer the following theory of justification:
Foundationalists generally tend to argue that there must be some set of epistemologically basic propositions or else the process of justification will always lead to an infinite regress, like a four-year old constantly asking "Why?" See the regress argument in epistemology.
Historically, two varieties of foundationalist theories were rationalism (or Rationalism, or Continental Rationalism, to refer to the historical movement) and empiricism (or Empiricism, or British Empiricism[?]). Strictly speaking, neither empiricism nor rationalism is committed to foundationalism (it is possible to be an empiricist coherentist, for example, and that was a common epistemological position in 20th century philosophy).
Rationalism is the general name for epistemological theories that maintain that the reason is the source and criterion of knowledge. Rationalists generally hold that so-called truths of reason are the (most important) epistemologically basic propositions. Rene Descartes famously held that some of these truths are known innately and therefore constitute epistemologically basic innate knowledge.
Empiricism is the general name for epistemological theories that maintain that sensation reports are the source and criterion of knowledge. Classical empiricists generally held that such reports are indubitable and incorrigible and therefore worthy of serving as epistemologically basic propositions.
Alternatives to foundationalism include coherentism[?] and reliabilism (though this has sometimes been construed as an unusual variant of foundationalism). Contextualism[?] (or, in a stripped-down version, the blind posits theory[?]) is the epistemological version of relativism; relativism is more often regarded as a theory of truth than as a theory of justification or knowledge.