Skepticism is the philosophical position that holds that knowledge is impossible or that we cannot be certain of anything.

Pyrrho of Elis (c. 360-270 BCE) is considered the father of skepticism. He argued that all beliefs are equally valid and that it is impossible to know anything for certain.

The three main forms of skepticism are methodological, epistemological, and metaphysical. Methodological skepticism questions the reliability of our methods of acquiring knowledge, epistemological skepticism questions the possibility of knowledge itself, and metaphysical skepticism questions the existence of an external world.

Methodological skepticism argues that our senses, reason, and memory are all unreliable sources of knowledge. Therefore, we cannot be certain of anything we know.

The regress argument states that all knowledge is ultimately based on beliefs that cannot be justified by other beliefs. This leads to an infinite regress, which means that we can never be certain of anything.

The brain in a vat argument states that we could be brains in a vat, being fed information by a mad scientist. This means that we could not be certain of anything we know, because our experience could be entirely illusory.

Foundationalism is the view that there are certain basic beliefs that are self-evident or indubitable. These beliefs can then be used to justify other beliefs, which can in turn be used to justify still other beliefs. This process can continue until we have a system of beliefs that is coherent and comprehensive.

The main problem with foundationalism is that it is circular. The basic beliefs that are supposed to justify all other beliefs are themselves justified by other beliefs, and so on. This leads to an infinite regress, which means that we can never be certain of anything.

Coherentism is the view that all beliefs are justified by their coherence with other beliefs. This means that a belief is justified if it is consistent with the rest of our beliefs and if it helps to explain our experience.

The main problem with coherentism is that it is circular. The beliefs that are supposed to justify other beliefs are themselves justified by other beliefs, and so on. This leads to an infinite regress, which means that we can never be certain of anything.

Pragmatism is the view that all beliefs are justified by their usefulness. This means that a belief is justified if it helps us to achieve our goals and if it makes our lives better.

The main problem with pragmatism is that it is too broad. It allows for the justification of any belief, no matter how bizarre or irrational. This makes it difficult to distinguish between true and false beliefs.

Fallibilism is the view that all beliefs are fallible. This means that even our most cherished beliefs could be wrong. Fallibilism is often contrasted with foundationalism, which holds that there are certain basic beliefs that are indubitable.

The main problem with fallibilism is that it is self-defeating. If all beliefs are fallible, then this includes the belief that all beliefs are fallible. This means that we cannot be certain of anything, including the belief that all beliefs are fallible.

Whether or not it is possible to overcome skepticism is a matter of opinion. There is no one right answer to this question. Some people believe that it is possible to overcome skepticism by finding a foundation for knowledge that is certain and indubitable. Others believe that skepticism is an unavoidable part of the human condition and that we can never be certain of anything.