The Milesian protophilosophy was an important phase in the development of Western thought. The first philosophical ideas of the origin and the nature of the world arose from the mythological images. The author tries to show, that the Milesian conceptions do not draw on the particular Greek myths, but on the archaic mythology embodying various mythological motives - the archetypes. The latter emerge spontaneously from human unconciousness and become a part of consciousness. Thales\' idea, that "water is the origin of all tings... and therefore the earth floats on water", is the expression of mythical experience based on the archetype of chaos. Its archetypal image is "the primal water" as the source of the arising world. Similarly there is an analogy between Anaximanderś apeiron and the archetype of chaos. The transition from the mythical-imaginative thought to rational and abstract one is represented also by Anaximenes, who also makes use of various archetypes (the similarity between the air and the archetype of chaos). The mythical-imaginative thought differs from rational conceptual thought in that in the former the part is identical with itself as well as with the whole, while in the latter the relationship between the part and the whole is dichotomical. The Greek thought developes into a purely dualistic way of thinking, which is fully manifested in Parmenides.