We all know intimately the passage of time. Life is transitory: hours fly by, days merge into years. Our personal experience seems always located in time. "Now" possesses an immediate presence and reality that past and future lack. But memories endure, often repossessing us with vivid detail and feeling. And hopes and fears can transform the present with images of beckoning paradises or ominous hells. While ever in the present, our awareness and imagination transcend it. Yet we know we are not the masters of time; rather it restricts and coerces us. Though awareness and conceptions of time are products of the human mind, time itself seems to possess an existence apart, its passage impersonal and inexorable. As an old Italian proverb put it, "Man measures time and time measures man." This intimate and personal, yet aloof and detached character constitutes the paradox of human time.