Non-rational in Nietzsche, Heidegger and Foucault

"What a human being is" and "what he will be in the future" are questions that can be asked especially by philosophy. However, nowadays in which these questions debated, the examination here focuses on the rational and the non-rational appearances of human beings. Then, here, the question is neither "what a human being is now" or "what he will be in the future"; rather in order to make preparation for these questions, the abilities of human beings, such as sensation, emotion, will, thinking, and reason, and their relations with each other are being examined in the context of Nietzsche, Heidegger, and Foucault. Though this study especially focuses on the non-rational, in order to have a definite picture of reason, in the Introduction, the ideas of some philosophers starting from Descartes to Hegel have been examined. Next, the thoughts of the philosophers who explicitly discuss on the non-rational have been examined. Nietzsche has mentioned about the inability and the rise of the reason, and that like every other thing, reason also has a becoming process. Heidegger has added another dimension to the reason with his idea "essential thinking" (das wesentliche Denken). And, Foucault has examined the power of the reason with madness. Thus, whether the reason and the non-rational can limit the world and especially human beings has been argued/discussed in the context of "causality" and thoughts of these philosophers. If so, we can say that although this study focuses on the non-rational, it is made only as the relationship of reason considered (it could be possible only by taking into consideration the reason). Thus, it has been attempted to show that the reason is not unconnected from the human appearances/faculties/abilities such as sensation, emotion, desire, madness, "essential thinking" which expressed here as non-rational, even (it) is related to their deepest ground. As a result, it has been tried to show that the reason can neither be able to encircle them from the beginning to end nor 'exist' without them. In this case, it has been attempted to justify that representation of an absolute reason is impossible, also the boundaries for world and for human cannot be drawn.