Recursion is a basic attribute of human thought, an underlying pattern that is without any source but itself. It is frequently found in the two most basic expressions of our mental workings, language and mathematics. Whether it be embedded sentences or fractals, the recurring theme is recursion.
Religion and reason, two common expressions of human thought, also feature this self-defining quality. The cycle of reincarnation and circular reason are obvious examples, but definitions of God and the axioms of logic are even more profound examples of the phenomenon.
Like most basic features of reality, recursion simply is, and we can only define it in terms of itself.