On the mountains of truth you can never climb in vain: either you will reach a point higher up today, or you will be training your powers so that you will be able to climb higher tomorrow.
Truth is a mobile army of metaphors, metonyms, anthropomorphisms, in short a sum of human relations which have been subjected to poetic and rhetorical intensification, translation and decoration […]; truths are illusions of which we have forgotten that they are illusions, metaphors which have become worn by frequent use and have lost all sensuous vigour […]. Yet we still do not know where the drive to truth comes from, for so far we have only heard about the obligation to be truthful which society imposes in order to exist" from, "On Truth and Lying in a Non-Moral Sense".
Mathematics would certainly have not come into existence if one had known from the beginning that there was in nature no exactly straight line, no actual circle, no absolute magnitude.
We do not belong to those who only get their thought from books, or at the prompting of books, -- it is our custom to think in the open air, walking, leaping, climbing, or dancing on lonesome mountains by preference, or close to the sea, where even the paths become thoughtful.
Pity is the most pleasant feeling in those who have not much pride and have no prospect of great conquests; for them the easy prey - and that is what all who suffer are - is enchanting.