Full Idea
Thoughts are merely signs, as words are signs for thoughts.
Gist of Idea
Thoughts are signs (just as words are)
Source
Friedrich Nietzsche (Unpublished Notebooks 1882-84 [1883], 5[1]272)
Book Reference
Nietzsche,Friedrich: 'Fragments from the period of 'Zarathustra' (v 14)', ed/tr. Loeb/Tinsley [Stanford 2019], p.196
A Reaction
The obvious question he invites is 'signs of what?'. His point must be that most thinking is both non-verbal and non-conscious, which he took to be true even of intellectual thought. I sympathise with his view.