I am working on the concept of 'doubles' in literature. I would like to quote the following extract that was sent via the Wordsmith account. Does anyone know where the quote was taken from and what the best book is to look up?

Emy:

Why should I fear death? If I am, death is not. If death is, I am not. Why
should I fear that which cannot exist when I do? -Epicurus, philosopher (c.
341-270 BCE)