History will judge John Archibald Wheeler as one of the towering intellects of the twentieth century. His career spanned the transition from the celebrated Golden Age of physics to the New Physics associated with the Space Age, the information revolution and the technological triumphs of quantum and particle physics. His contributions, ranging from trailblazing work in nuclear physics to general relativity and astrophysics, are too numerous to list here. His influence on three generations of physicists is immense.

But Wheeler has been more than a brilliant and influential theoretical physicist. The decision to hold a symposium Science and Ultimate Reality in his honor reflects the fact that he is also an inspiring visionary who brought to physics and cosmology a unique style of thought and mode of reasoning, compared by Jaroslav Pelikan in this volume to that of the Greek philosopher Heraclitus.

“Progress in science,” Wheeler once remarked to me, “owes more to the clash of ideas than the steady accumulation of facts.” Wheeler has always loved contradiction. After all, the Golden Age of physics was founded on them. The theory of relativity sprang from the inconsistency between the principle of relativity of uniform motion, dating back to Galileo, and Maxwell's equations of electromagnetism, which predicted a fixed speed of light. Quantum mechanics emerged from the incompatibility of thermodynamics with the continuous nature of radiation energy.