Voyages of Discovery: what are our certainties, when we, and what we find, are constantly in flux?

A swifter and more obvious stream lays hold of mankind, for although the waters of a river flee, its appearance is the same. However, as the years of a man’s life slip away, his appearance is so different and so altered that after a short time he cannot be recognized, even by friends and kin. Thus, as boyhood obscures infancy, and adolescence obscures boyhood, and adulthood, which the naturalists falsely call permanent, obscures both, at length, old age removes all other ages the same way….

Now imagine yourselves returning to the cities you once inhabited. I ask, what do you suspect? Perhaps you will see well-known towers again and recognize ancient walls, although even they may soon fall to ruin. The places endure, the rivers flow by; and mountains stand. Hunt for the people you once knew. I do not know how it happens, but almost all of them will have disappeared. A great amazement will seize you as you enter that same city which has yet become another, and you may agree with Heraclitus, who said we enter the same city twice, but do not enter it.

Francesco Petrarch, On Religious Leisure, trans. Susan Schearer