Internalism holds that the justification of a belief is determined solely by the believer's mental states, such as their evidence, reasons, and cognitive processes.

Externalism holds that the justification of a belief is determined solely by external factors, such as the evidence available, the testimony of others, and the social and cultural context.

Coherentism is an internalist theory of justification that holds that a belief is justified if it is coherent with the believer's other beliefs and evidence.

Reliabilism is an externalist theory of justification that holds that a belief is justified if it is formed by a reliable process, such as perception or memory.

The main objection to internalism is that it is too subjective, as it relies solely on the believer's mental states to determine the justification of a belief.

The main objection to externalism is that it is too objective, as it relies solely on external factors to determine the justification of a belief, ignoring the believer's mental states.

René Descartes is most closely associated with internalism, as he argued that the only thing that can be known with certainty is one's own thoughts and experiences.

John Locke is most closely associated with externalism, as he argued that all knowledge comes from experience and that the mind is a blank slate at birth.

Internalism is opposed to skepticism, as it holds that there are some beliefs that can be known with certainty, such as one's own thoughts and experiences.

Externalism is opposed to skepticism, as it holds that there are some beliefs that can be known with certainty, such as those that are based on reliable evidence.

The Cogito ergo sum argument is an internalist argument against skepticism, as it argues that the only thing that can be known with certainty is one's own thoughts and experiences.

The Problem of Evil is an externalist argument against skepticism, as it argues that the existence of evil in the world is evidence that there is a God who is either not all-powerful or not all-good.

The internalism/externalism debate has implications for our understanding of knowledge, justification, and truth, as it raises questions about the role of the believer's mental states and external factors in determining the justification of a belief.

The internalism/externalism debate is likely to continue for many years to come, as there are strong arguments on both sides of the issue and no clear consensus is likely to emerge in the near future.

All of the above are promising avenues for future research on internalism and externalism, as they offer the potential to deepen our understanding of these important philosophical issues.