For me, this formulation acknowledges the absolute reality of our real human condition. We do create a world, into which we project our purposes, and in which, at least sometimes, our purposes (for good or ill) prevail.
But ultimately, we do not live in the world we make. However much we most immediately live in the human world of our own creation, we ultimately exist in and depend upon a world that we did not create, the world of Nature. The world (for those who see it this way) that God created. And in that world, upon which everything depends, our "purposes" are intrusions that can have the most deadly consequence. Our powers are such, it now appears, that we can put not only the world that we create at risk, but the world of Nature, too. Global warming and the BP blowout are only two of the most recent and most dramatic signs that this is so.
So, I would like to withdraw from any claim that I (or we) are actually charged in this existence with the duty, or responsibility, or opportunity to achieve some "end." Some "purpose."
I was brought up as an Episcopalian. I scan my list of ends to be achieved (for good or ill), and read wonderful statements like that of Peter Douglas, and come back, always, to "there is no end to life," and to Micah 6:8:
He has showed you, O man, what is good. And what does the LORD require of you? To act justly and to love mercy and to walk humbly with your God.
No real "end" or "purpose" outlined here.