 Foundationalists are united in their conviction that there must be a kind of justification that does not depend on the having of justification for other beliefs. They nevertheless disagree radically among themselves as to how to understand foundational justification. In the latter part of the 20th century, the rise of externalist epistemologies has generated even more fundamentally different versions of foundationalism. It will not be possible to survey all of the strikingly different analyses or theories that have been offered of foundational justification. In what follows we will examine a few of the more prominent versions of classical and contemporary internalist and externalist foundationalism.