Final answer:
Plato first claimed that knowledge is justified true belief. His account remained the standard until challenged by Edmund Gettier in the 1960s, leading to the development of Gettier cases and the recognition of the Gettier problem, which revealed issues with the JTB account.
Step-by-step explanation:
The Philosopher Who Claimed Knowledge is Justified True Belief
The philosopher Plato first claimed that knowledge is justified true belief (JTB). This definition, also known as the traditional account of knowledge, asserts that a person S knows proposition P if and only if it is true, the person believes it, and they are justified in their belief. Plato's theory was the standard for over two millennia until Edmund Gettier challenged it in the 20th century with Gettier cases, which demonstrate situations where someone may have a justified true belief yet still not possess knowledge, highlighting the inadequacy of the JTB account—a problem referred to as the Gettier problem.
Plato's analysis, which was accepted until the 1960s, suggested that to declare knowledge, one must have belief, truth, and justification. However, fixes to the JTB account have been proposed post-Gettier, illustrating the complexity of the analysis of knowledge and how it continues to evolve in the realm of epistemology.