Every man takes the limits of his own field of vision for the limits of the world.

[Jeder hält das Ende seines Gesichtskreises für das der Welt.]

Arthur Schopenhauer (1788-1860) German philosopher

Parerga and Paralipomena, Vol. 2, ch. 26 “Psychological Observations [Psychologische Bemerkungen],” § 338 (1851) [tr. Saunders (1890)]
    (Source)

(Source (German)). Alternate translation:

Everyone regards the limits of his field of vision as those of the world.
[tr. Payne (1974)]