According to ancient tradition, philosophy began when Thales of Miletus correctly predicted the solar eclipse of 585 BCE. Ancient historians of philosophy speculated about the reasons for the birth of philosophy in Miletus. The Milesians shared an outlook on the world that indicates the beginnings of philosophical ways of thinking about reality.
Curd explains that part of this was "a willingness to speculate and give reasons based on evidence and argument" (Curd 2011, 2). Another major part was "a commitment to the view that the natural world (the entire universe) can be explained without needing to refer to anything beyond nature itself" (Curd 2011, 2). Hence philosophy began when superstition and mythology became apparently insufficient to explain phenomena which observation, experimentation, and reasoning could predict or explain.
Science and philosophy came from a specific way of thinking - and by extension talking - about the world. This method of discourse required evidence, logic, and experimentation. Problems which superstition and mythology had previously answered were now within the domain of human knowledge. Why do the stars move in the manner that they do? Mathematical principles can explain and predict that. What is the stuff that the world is made of? Various theories can account for certain features of nature, and the theory that is most consistent with observations of the natural world is best. This way of thinking allowed for disputation and argumentation, making it possible for human knowledge to advance. Prior to this way of thinking, people accepted theories because of who gave them (namely the gods). Now evidence and logical consequence became the sources of merit for explanations of the world.