It is widely accepted that philosophy started in the VI century BC as a
transition from irrational thinking to the rational or philosophical thinking. This
transition, however, did not take place overnight, but just the opposite. In the same
way that Parmenides was a philosopher even though we only have a poem written by
him, Plato used myths as a part of his explanations of several philosophical points.
These situations already show what we try to demonstrate here: the so-called rational
thinking –which usually belongs to philosophy - is not so pure nor rational. There
are several important cases in which irrational concepts, such as demons, ghosts and
spirits, were used in order to create philosophical arguments. The main figures of the
philosophical panorama (i.e. Socrates, Descartes and Hegel) used these concepts that
seem to belong to a different context rather than to philosophy. There is a pattern that
repeats in these three philosophers –all of them lived in a period of transition. Perhaps
these periods needed this kind of “out of the way” concepts to allow thinkers to face
the new challenges they had to encounter.