esse

esse \ES-se; Eng. ES-ee\, noun:

being; existence.

The esse of the life of every man, which he has from his father, is called the soul, and the existence of life thence derived is called the body.
-- Emanuel Swedenborg, The Earths in Our Solar System, 1758

According to Berkeley, the esse of things is percipi. They exist as they are perceived.
-- Thomas Love Peacock, Nightmare Abbey, 1818

Esse comes from the Latin word of the same spelling meaning "to be." It has been in English since the 1600s.