Appearances to the mind are of four kinds

According to the ancient phrygian  philosopher Epictetus, appearances to the mind are of four kinds:

(a) things either are what they appear to be,

(b) or they neither are, nor appear to be,

(c) or they are, and do not appear to be,

(d) or they are not, and yet appear to be.

Epictetus also added this: rightly to aim in all these cases is the wise man's task.