For all its material advantages, the sedentary life has left us edgy, unfulfilled, even after 400 generations in villages and cities, we haven't forgotten: The open road still softly calls like a nearly forgotten song of childhood.

Much of human history can, I think, be described as a gradual and sometimes painful liberation from provincialism, the emerging awareness that there is more to the world than was generally believed by our ancestors.

By exploring other worlds we safeguard this one. By itself, I think this fact more than justifies the money our species has spent in sending ships to other worlds. It is our fate to live during one of the most perilous and, at the same time, one of the most hopeful chapters in human history.

Science cuts two ways, of course; its products can be used for both good and evil. But there's no turning back from science. The early warnings about technological dangers also come from science.

Even today the most jaded city dweller can be unexpectedly moved upon encountering a clear night sky studded with thousands of twinkling stars. When it happens to me after all these years it still takes my breath away.

Both the Freudian and the Platonic metaphors emphasize the considerable independence of and tension among the constituent parts of the psyche, a point that characterizes the human condition.

Those with the courage to explore the weave and structure of the Cosmos, even where it differs profoundly from their wishes and prejudices, will penetrate its deepest mysteries.