Should we not assume that just as the eye, the hand, the foot, and in general each part of the body clearly has its own proper function, so man too has some function over and above the functions of his parts? What can this function possibly be? Simply living? He shares that even with plants, but we are now looking for something peculiar to man. Accordingly, the life of nutrition and growth must be excluded. Next in line there is a life of sense perception. But this, too, man has in common with the horse, the ox, and every animal. There remains then an active life of the rational element.... The proper function of man, then, consists in an activity of the soul in conformity with a rational principle or, at least, not without it.
The Birth of Rational Man
IN APRIL OF 1970 THE APOLLO 13 moon mission went awry. A tank of liquid oxygen exploded, depriving the command module Odyssey of the oxygen needed for the fuel cells that powered the craft and for the air the astronauts breathed. A nightmarish succession of problems afflicted the crew and ground control in Houston, problems that had to be solved from two hundred thousand miles away under the intense time pressure caused by the dwindling oxygen and power. The biggest difficulty, of course, was working out the complex calculations and procedures that would safely get the crew back to earth in a crippled ship. As the popular film Apollo 13 showed, each crisis was met and overcome by sheer innovative brilliance, extemporaneous engineering, and occasional luck. The crew made it back to earth alive, and what could have been a disaster for NASA was eventually recognized as one of its finest hours.
This triumph of nerve and skill over calamity has its ultimate origins in a new way of looking at the world that arose in ancient Greece. At one level, the science and technology that make space travel possible are obviously a culmination of the long, halting development of procedures for acquiring knowledge about nature and