I etch a pattern of geometric shapes onto a stone. To the uninitiated, the shapes look mysterious and complex, but I know that when arranged correctly they will give the stone a special power, enabling it to respond to incantations in a language no human being has ever spoken. I will ask the stone questions in this language, and it will answer by showing me a vision: a world created by my spell, a world imagined within the pattern on the stone.

A few hundred years ago in my native New England, an accurate description of my occupation would have gotten me burned at the stake. Yet my work involves no witchcraft: I design and program computers. The stone is a wafer of silicon, and the incantations are software.