Foundationalism is a philosophical theory that suggests knowledge is built upon a foundation of certain, indubitable beliefs. These basic beliefs serve as the starting point for constructing further knowledge, much like a building rests on a solid base. Foundationalists argue that some beliefs are self-evident or require no further justification, providing stability to our understanding of the world. In foundationalism, the goal is to avoid skepticism by establishing a secure framework for knowledge. This approach contrasts with coherentism, which holds that beliefs are justified by their coherence with other beliefs rather than by a foundational basis. Key figures in foundationalism include philosophers like René Descartes and John Locke.