A Druid was a member of the high-ranking professional class in ancient Celtic cultures. Best remembered as religious leaders, they were also legal authorities, adjudicators, lorekeepers, medical professionals and political advisors.

Druids were philosophers and called their doctrine of the immortality of the soul and reincarnation or metempsychosis Pythagorean, who were considerably influenced by mathematics and mysticism and believed that the soul does not die and that after death it passes from one body into another.

Numbers have two forms, the even and the odd, and a third, resulting from the mixture of the two, the even-odd. This third species is one itself, for it is both even and odd.

One, or unity, is the essence of number, or absolute number, and so comprises these two opposite species. As absolute number it is the origin of all numbers, and so of all things.