BIJOB BEYTULHIKME INTERNATIONAL JOURNAL OF PHILOSOPHY, cilt.11, sa.2, ss.521-531, 2021 (ESCI)
This study will focus on the examples in Edmund L. Gettier's article titled "Is Justified True Belief Knowledge?", which addresses two cases to draw our attention to the lack of a tripartite conception of knowledge, and on some examples in the article titled with "Knowledge: Undefeated Justified True Belief" by Keith Lehrer and Thomas Paxson who advocate one of the quadripartite conceptions of knowledge to overcome these shortcomings. Firstly, this study will try to determine what kind of natural deduction the examples in these articles are, then show whether these deductions are valid by using direct and indirect proving methods.