Edmund Gettier's Is Justified True Knowledge?

One of the most widely accepted definitions of knowledge was once that of knowledge being justified true belief (JTB). It is used to define propositional logic which involves knowing whether something is or is not true. Specifically, it sets out that knowledge is a belief which happens to be true such that there exists significant justification for holding said belief. This supposed definition can be traced back to Plato’s Theaetetus and remained unchallenged until Edmund Gettier published a paper in 1963 entitled ‘Is Justified True Belief Knowledge?’ In it, Gettier demonstrates that the three conditions which must hold for knowledge outlined in the JTB definition are not sufficient for knowledge to be attained. His short paper caused a major

This means that S’s belief in P cannot be caused by falsehoods. On the surface it seems like an excellent contender to solve the Gettier problem. While false beliefs are already ruled out, this condition eliminates true beliefs based on false premises too. This condition also appears to solve Gettier’s counter examples for JTB. In the Smith and Jones job hunt, Smith’s belief that the man with ten coins in his pocket will get the job originates from his false thought that Jones will get the job. As a result, the fourth condition is not satisfied and so knowledge cannot be claimed. However, Robert Chisholm demonstrates in his famous ‘Sheepdog’ example that this too is an unsatisfactory definition for knowledge. Consider a field where in the middle is a dog dressed as a sheep. As a man drives by, he the forms the justified belief based on his perception that there is a sheep in the field. His belief turns out to be true as behind rocks in the field there are some sheep which are hidden from the man. Furthermore, the no false lemma condition is satisfied because his belief is not based on any falsehood, only from his perception. Unfortunately, one cannot say the man knew there were sheep in the field as he was unaware about the obscured sheep, only the disguised dog. This is yet another example of a lucky guesser. While this proposed solution attempts to solve the Gettier problem, it does so unsuccessfully. Another solution is