Edmund Gettier is an American philosopher best known for his work in epistemology, the study of knowledge. In 1963, he published a short paper titled "Is Justified True Belief Knowledge?" which challenged the traditional definition of knowledge as justified true belief. His arguments presented scenarios, now known as Gettier cases, where individuals had beliefs that were justified and true, yet intuitively did not qualify as knowledge. Gettier's work sparked significant debate in philosophy, leading to the development of new theories about the nature of knowledge. His influence is evident in ongoing discussions about the conditions necessary for knowledge, prompting philosophers to refine their understanding of concepts like justification and truth.