Belli açılardan, biri klasik diğeri modern felsefenin öncüsü olarak kabul edilen Platon ve Descartes birbirilerinden yalnızca çağları bakımından değil; ruh, beden ve töz anlayışları bakımından da farklılık gösterir. Bununla birlikte, hakikati ararken temel aldıkları modus operandi (çalışma şekli, yöntem) bakımından ise oldukça yakın anlayışlara sahip oldukları iddia edilebilir. Platon psykhe’nin varlığa açılma zeminini ortaya koyarken, Descartes ise ben-Tanrı-uzamlı cisimler anlayışını temellendirirken epistemolojiyi merkeze almıştır. Bu bağlamda, varlığa farklı derecelerde epistemolojik bir karakter kazandırmaları bakımından filozofların karşılaştırılabileceğini söylemek mümkün olabilir. Bu açıdan bu çalışma Batı Felsefesi tarihinde önemli değişimler yaratan Platon ve Descartes’ın ontoloji ile epistemoloji arasında kurdukları farklı ve benzer ilişkileri ve epistemolojik çözümlemelerini konu edinmektedir.
In this study, we tried to reveal what philosophy is and its function based on the concepts. Man, who is a reasonable being, needs philosophy. The philosophy that man needs is the one compatible with reality. Philosophy, which critically examines the concepts put forward about human, universe and existence, is a mental effort. The functions of philosophy towards concepts and beliefs are analysis, synthesis and criticism. Philosophy explains concepts, and critically evaluates beliefs. It tries to justify the conclusions based on explanation and criticism. Philosophy examines the main characteristics of the relationships among existence, human and human-being. At this stage, philosophy abides by concepts whose one side scrutinize the beings. Philosophy, which is also accepted as the process of analysing the structure of thought, turns to language and therefore to the analysis of concepts as the appropriate ground for realizing this function. Sciences also use concepts, but only philosophy does the analysis of the concepts. Individually, Philosophy performs this function based on the human reason. Because philosophy is an activity based on reason and it is individual. Despite the objective nature of science, philosophy is subjective. As an individual activity, philosophy is based on the individual's ability to produce and create based on his/her reasoning. What philosophy produces and creates on the occasion of individual contemplation are concepts. Concepts are what the philosopher thinks about by discovering. The philosopher, who has the power to produce and create concepts, is concept-friendly. Therefore, philosophy can be described as a discipline that includes creating concepts or as knowledge acquired through pure concepts.