“What if a demon crept after you and said: "This life as you now live it you will have to live once more and innumerable times more"?”
— Friedrich Nietzsche, The Gay Science, §341
What this quote means
The original statement of eternal recurrence, posed as "the heaviest weight." Nietzsche asks whether you could affirm your life so completely that you would will its infinite return — the existential test behind amor fati.
The idea behind it
Eternal Recurrence — Nietzsche's thought-experiment: if you had to live your life over and over, identically, forever — could you affirm it?
The Gay Science is public domain; attribution verified. Confidence: high.