this double experience
of mutation and recurrence,
an experience at once
sentimental and scientific,
soon brought with it a very great thought,
perhaps the greatest thought ever lit upon,
and which was the chief inspiration for lucretius.
it is that all we observe about us, and ourselves also,
may be so many passing forms of permanent substance.
this substance, while remaining the same
in quantity and in inward quality, is
constantly redistributed. in it's redistribution
it forms those aggregates we call things,
and which we find constantly disappearing
and reappearing.

george santayana