We have peered into a new world and have seen that it is more mysterious and more complex than we had imagined. Still more mysteries of the universe remain hidden. Their discovery awaits the adventurous scientists of the future. I like it this way.

"In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities."

One of the curious features of modern physics is that in spite of its overwhelming success in explaining a vast range of physical phenomena from quark to quasar, it fails to give us a single metaphor for how the universe really works.

Few men, whatever their creed, would now seek their geology in the books of their religion, or, on the other hand, would fancy that the laboratory or the microscope could help them to penetrate the mysteries which hang over the nature and the destiny of the soul of man. ... We live in a small, bright oasis of knowledge, surrounded on all sides by a vast, unexplored region of impenetrable mystery.

I often liken the process of physics research to solving a jigsaw puzzle. As we put together pieces to form patches, a certain image of the overall picture emerges, but until the game is sufficiently progressed, we are not quite sure. I feel much the same way about the wealth of signs for new particles. We have patches that have been put together, but we are not quite sure how all pieces will fit together into a coherent whole. There are also certain pieces which do not seem to fit into any patches at all. For the most part, the experimental findings have not been completely unexpected, but there have been certain surprises that I, for one, had not foreseen. This is what makes particle physics exciting and tantalizing. At moments of despair and frustration, I feel as though somebody has scrambled two boxes of jigsaw puzzles for me to put together.

It's my belief that the Universe possesses, in its essence, fractal properties of a very complex sort and that the pursuit of science shares those properties. It follows that any part of the Universe that remains un-understood, and any part of scientific investigation that remains unresolved, however small that might be in comparison to what is understood and resolved, contains within it all the complexity of the original. Therefore, we'll never finish. No matter how far we go, the road ahead will be as long as it was at the start, and that's the secret of the Universe.

It is a great adventure to contemplate the universe, beyond man, to contemplate what it would be like without man, as it was in a great part of its long history and as it is in a great majority of places. When this objective view is finally attained, and the mystery and majesty of matter are fully appreciated, to then turn the objective eye back on man viewed as matter, to view life as part of this universal mystery of greatest depth, is to sense an experience which is very rare, and very exciting. It usually ends in laughter and a delight in the futility of trying to understand what this atom in the universe is, this thing — atoms with curiosity — that looks at itself and wonders why it wonders. Well, these scientific views end in awe and mystery, lost at the edge in uncertainty, but they appear to be so deep and so impressive that the theory that it is all arranged as a stage for God to watch man's struggle for good and evil seems inadequate.

Anyone who compares the bibliography with the reprinted papers will notice that mathematics and physics have not been given equal treatment. There is a strong bias in favor of mathematics. The bias arises from the fact that mathematical papers, provided that are correct and not trivial, have permanent value, whereas most papers in physics journals are ephemeral. For this reason, it is customary to publish complete collected works of mathematicians but only selected works of physicists.