Full Idea
Only when the human being has finally attained knowledge of all things will he have known himself. For things are merely the boundaries of the human being.
Gist of Idea
Things are the boundaries of humanity, so all things must be known, for self-knowledge
Source
Friedrich Nietzsche (Dawn (Daybreak) [1881], 048)
Book Reference
Nietzsche,Friedrich: 'Dawn (Daybreak) (v 5)', ed/tr. Smith, Brittain [Stanford 2011], p.38
A Reaction
This seems to be a rather externalist view of the mind. If philosophy aims to disentangle mind from world then good knowledge of the world seems to be required.
Related Idea
Idea 2352 The job of the philosopher is to distinguish facts about the world from conventions [Putnam]