Thales’ philosophical proposition, where “the originality (arche) of the world is water”, not only follows the traditional curiosity about the creation of the ancient Greek mythology, but also indicates the basic characters of the Western philosophy, regarding the ontology as the basic content, the theory related to ultimate reality, and tying to the principle of reason. The proposition of Water signifies the transfer of human’s world view from theological angle of view to naturalism, from theology to philosophy, however, the proposition of arche marks the beginning of philosophers’ pursuit of the identity and the belief in the realest being. Since then, arche became the first category of the western philosophy. The relation of One and multiplicity it contains becomes the perpetual pursuit for the western philosophy. The ancient Greek chose the belief in One and the road to the truth, which brings about the general character of the western philosophy: logic speculative and the rationalist tradition lasting thousands of years. 