Internalism is a philosophical position in epistemology that asserts that the justification for a belief must come from factors internal to a person's own mental states. This means that individuals can only rely on their own thoughts, feelings, and experiences to justify their beliefs, rather than external factors or influences. In contrast to externalism, which allows for justification based on outside evidence or conditions, internalism emphasizes personal reflection and introspection. This approach highlights the importance of an individual's perspective and cognitive processes in understanding how beliefs are formed and justified, making it a significant topic in discussions about knowledge and belief systems.