Full Idea
We simply lack any organ for knowledge, for 'truth'; we 'know' [das Erkennen] (or believe or imagine) just as much as may be useful in the interests of the human herd, the species; and this 'utility' is ultimately also a mere belief.
Gist of Idea
We have no organ for knowledge or truth; we only 'know' what is useful to the human herd
Source
Friedrich Nietzsche (The Gay (Joyful) Science [1882], §354)
Book Reference
Nietzsche,Friedrich: 'The Gay Science', ed/tr. Kaufmann,Walter [Vintage 1974], p.300
A Reaction
[Section §354 is fascinating!] An odd idea, that we can only have truth is we have an 'organ' for it. It seems plausible that the whole brain is a truth machine. This seems like pure pragmatism, with all its faults. Falsehoods can be useful.