Appearances to the mind are of four kinds. Things either are what they appear to be; or they neither are, nor appear to be; or they are, and do not appear to be; or they are not, and yet appear to be. Rightly to aim in all these cases is the wise man’s task.

Epictetus (c.55-c.135) Greek (Phrygian) Stoic philosopher

The Discourses (c. AD 101-108)