THE CAVE (403 pp.)Robert Penn WarrenRandom House ($4.95).
Plato's famed metaphor of the cave (in The Republic) makes a cruel point: men see shadow and think they see substance. The image is brutalcave dwellers chained underground from childhood, unable to see anything except fire shapes on a rock wall, never suspecting the existence of the objects that cast the shadows. When one of them is dragged into the open air and forced to stare first at the objects themselves, then at the agonizing reality of the sun, he fights to disbelieve his senses. So, when their hidden natures are thrust into the...