This special feature marks the first collaboration between FEED and Edge, John Brockman's invitation-only Internet forum, where hundreds of the world's leading scientists and thinkers share their thoughts on issues ranging from the meaning of numbers to genetics to affirmative action. We'll be excerpting two or three articles a month from Edge, and creating special Loop discussions where our readers can add their own observations to Edge's challenging and adventuresome debate. Our first installment is a series of answers to the question, "What was the most important invention of the past two thousand years?" The contributors include Freeman Dyson, Richard Dawkins, and Joseph Traub. Readers can visit the Edge site for even more nominations, and can post their own suggestions in the Loop.