Power moves, warms and threatens all of us, and it is disturbing that power has become visibly problemmaJic and unpredictable. It expands with a relentless logic as men wrestle nature into strange shapes, vault into space and race to create new forms of wealth, persuasion and terror. It destroys the earth, menacing air arid water; even when it seems benign, as in medicine, it helps conjure the possibility of an over-populated planet. Yet it also seems curiously ineffective; ragged guerrillas defy great powers, students show contempt for wealth and for the state, black militants face force with defiance.