The paper deals with Heidegger’s separating the pre-socratic thinkers (namely Heraclitus and Parmenides) from the other Greek philosophers in his lecture What is philosophy? The reason is to be seen in that the former still lived in harmony with the original Greek conceiving of Being. Since Plato and Aristotle the philosophers have been gradually forgetting the Being and concentrated exclusively on existence (Dasein). However, this Heidegger’s hypothesis is not supported by any profound philosophical researches. In the lecture he is searching for a philosophical answer to his own philosophical question, an answer which he never found. Therefore, in his later writings he gave up trying to resolve the question of Being.