Immortality means endurance in time, deathless life on this earth and in this world as it was given, according to Greek understanding, to nature.... Against this background of nature's ever-recurring life ... stood mortal men, the only mortals in an immortal but not eternal universe ...
The mortality of men lies in the fact that individual life, with a recognizable life-story from birth to death, rises out of biological life. This individual life is distinguished from all other things by the rectilinear course of its movement, which, so to speak, cuts through the circular movement of biological life. This is mortality: to move along a rectilinear line in a universe where everything, if it moves at all, moves in a cyclical order.
The task and potential greatness of mortals lie in their ability to produce things - works and deeds and words - which would deserve to be and, at least to a degree, are at home in everlastingness, so that through them mortals could find their place in a cosmos where everything is immortal except themselves.