beliefs using some form of rationalization; an example would be that Night gives birth to Death, Sleep and Dreams. Transmigration of life, a belief of the Orphics, a religious cult originating from Thrace, had affected the thought of the 5th century BCE but the overall influence of their cosmology on philosophy is disputed. Pherecydes, a poet, magician, and contemporary of Thales, in his book describes a particular cosmogony, asserting that three gods pre-existed – a step towards rationality. General features The most important feature of pre-Socratic philosophy was the use of reason to explain the universe. The pre-Socratic philosophers shared the intuition that there was a single explanation that could explain both the plurality and the singularity of the whole – and that explanation would not be direct actions of the gods. The pre-Socratic philosophers rejected traditional mythological explanations of the phenomena they saw around them in favor of more rational explanations, initiating analytic and critical thought. Their efforts were directed at the investigation of the ultimate basis and essential nature of the external world. Many sought the material principle (arche) of things, and the method of their origin and disappearance. They emphasized the rational unity of things and rejected supernatural explanations, seeking natural principles at work in the world and human society. The pre-Socratics saw the world as a cosmos, an ordered arrangement that could be understood via rational inquiry. In their effort to make sense of the cosmos they coined new terms and concepts such as rhythm, symmetry, analogy, deductionism, reductionism, mathematization of nature and others. An important term that is met in the thought of several pre-Socratic philosophers is arche. Depending on the context, it can take various related meanings. It could mean the beginning or origin with the undertone that there is an effect on the things to follow. Also, it might mean a principle or a cause (especially in Aristotelian tradition). A common feature of the pre-Socratics is the absence of empiricism and experimentation in order to prove their theories. This may have been because of a lack of instruments, or because of a tendency to view the world as a unity, undeconstructable, so it would be impossible for an external eye to observe tiny fractions of nature under experimental control. According to Jonathan Barnes, a professor of ancient philosophy, pre-Socratic philosophy exhibits three significant features: they were internal, systematic and economical. Internal meaning they