Clay can be a metaphor for many things. I made it a metaphor for flesh and earth, and these are two kinds of generic givens of life, if you look at it poetically, biblically, the idea of the life of beings, of man, being transitory, the earth abides-ashes to ashes, dust to dust-man returns to earth, grows out of earth like a flower, wilts, goes back to the earth... We are frail, transitory creatures with aspirations of immortality, conscious of our inevitable death, and we have to deal with it somehow.
Stephen De Staebler