The greatest weight.-- What, if some day or night a demon were to steal after you into your loneliest loneliness and say to you: "This life as you now live it and have lived it, you will have to live once more and innumerable times more; and there will be nothing new in it, but every pain and every joy and every thought and sigh and everything unutterably small or great in your life will have to return to you, all in the same succession and sequence - even this spider and this moonlight between the trees, and even this moment and I myself. The eternal hourglass of existence is turned upside down again and again, and you with it, speck of dust!"Would you not throw yourself down and gnash your teeth and curse the demon who spoke thus?... Or how well disposed would you have to become to yourself and to life to crave nothing more fervently than this ultimate eternal confirmation and seal?
from Nietzsche's The Gay Science, s.341, Walter Kaufmann transl.
Four thoughts ...
It seems counter-intuitive to me to view eternity as linear. If it were linear then all of eternity would stretch out before I was born and forevermore after I die. How can this be? If eternity existed before I was born then the time would never arrive for me to be born. Thus eternity is circular and hence my belief in the Eternal Recurrence.
There is also eternity in a moment. A moment of action, now in the past, exists for eternity - is this not hard to deny? It cannot be changed and therefore exists forever, locked in time and space. As eons pass and eternity comes full circle this moment is replayed.
There is one fact that I cannot deny and that is that I exist. It is possible for me to exist. If it is possible once then it is possible again.
Life then becomes the very opposite of meaningless. We are locked into this circle of eternity forever therefore it is imperitive that, with all our energy, we make this life the best possible one we can.