Viriditas is a word coined by Hildegard von Bingen. She saw the notion of 'Viriditas', or Greenness, penetrating every aspect of life. This 'Greenness' was the very expression of Divine power on Earth. "The Word of God regulates the movements of the Sun, the Moon and the stars. The Word of God gives the light which shines from the heavenly bodies. He makes the wind blow, the rivers run and the rain fall. He makes trees burst into blossom, and the crops bring forth the harvest."
Since this extraordinary phenomenon called life could only be created by God, Hildegard believed, all that lives equally carried his Divine energy, or 'viritas':
Oh fire of the Holy Spirit,
life of the life of every creature,
holy are you in giving life to forms...
Oh boldest path,
penetrating into all places,
in the heights, on earth,
and in every abyss,
you bring and bind all together
From you clouds flow, air flies,
Rocks have their humours,
Rivers spring forth from the waters
And earth wears her green vigour
O ignis Spiritus Paracliti
This is the foundation upon which all her texts rest,
whether songs, visions or natural observations.*
*Quoted from: The Ecologist: The Cosmic Vision of Hildegard of Bingen.