One of the basic Martin Heidegger's questions is what are the roots and conditions, both philosophical and historical, that culminated in modern viewpoint transforming 'subiectum' into 'res cogitans' due to safeguard its privileged position as the only and rightful owner of the truth. As he looks into the history of metaphysics, he conceives of the tradition, which started with Plato's conception of idea and which had been consistently followed until Cartesian 'ego cogito' was set, as the ages of oblivion of being. 'Esse est percipi', to be means to make the world an object to confirm own potency. As Heidegger shows, this is only a secondary mode of human existence. The everyday being of 'Dasein' rather than its consciousness is the starting point of philosophy. That is why it should be led back to the question of being, which is also the only way to oppose humanism of modern technological society. Dasein's being-in-the-world is originally chaos and risk and therefore philosophy can never be crowned with certainty.