What We Believe But Cannot Prove: Today’s Leading Thinkers on Science in the Age of Certainty
Edited by John Brockman
Harper Perennial, 252 pp., paperback, $13.95
Chasing Spring: An American Journey Through a Changing Season
By Bruce Stutz
Scribner, 239 pp., $24
Pilgrim on the Great Bird Continent: The Importance of Everything and Other Lessons From Darwin’s Lost Notebooks
By Lyanda Lynn Haupt
Little, Brown, 276 pp., illustrated, $24.95
For the past eight years, the website www.edge.org  has tried to provoke its distinguished roster of contributors with a big, elegant question. Last year's question was this: What do you believe to be true even though you cannot prove it?
A hundred and nine prominent thinkers, including folks as accomplished as Richard Dawkins, Steven Pinker, Rebecca Goldstein, and Freeman Dyson, responded. Their answers are collected in a new book, ''What We Believe But Cannot Prove," and it makes for some astounding reading.
What do they believe (but can't prove)? Many believe there is an external reality independent of consciousness. Many believe life is pervasive in the universe. Several believe, in the words of neurologist Robert M. Sapolsky, that ''there is no God(s) or such a thing as a soul." Theoretician Judith Rich Harris believes the Neanderthals disappeared because Homo sapiens ate them. Two believe there is a God. One believes in true love. The longtime New Scientist editor Alun Anderson believes cockroaches are conscious. Harvard professor Daniel Gilbert believes you are true -- that is, he believes you have an inner life and a sense of self -- even though he cannot prove it.
Taken as a whole, this little compendium of essays will send you careening from mathematics to economics to the moral progress of the human race, and it is marvelous to watch this muddle of disciplines overlap. Will the human brain eventually be able to discover all there is to discover about the physical world? Or will there always be things that we will not know?
A few months before edge.org  proposed its 2005 question, former Natural History editor Bruce Stutz was recovering from heart-valve surgery in the torpid gloom of a Brooklyn winter. Dazed, drained of energy, and feeling suddenly that his ''most verdant years" were behind him, Stutz began yearning for spring.
He yearned not just for the material manifestations of the season, but for its sparkle, the ''transformative energy possessed by growing, blossoming, transmuting things." By the end of June he traveled almost 10,000 miles in a 1984 Chevy Impala, watching spring creep northward across the United States, seeing everything he could, and writing it all down.
Part travelogue, part environmental assessment, part midlife crisis, ''Chasing Spring" is as much about Stutz himself as it is about the season. He slogs from Louisiana to Arizona to Utah to Alaska, chatting with scientists, watching birds, testing his heart on mountain passes and in the tundra of the Arctic National Wildlife Refuge. By the end of his odyssey, the spring of Arctic Alaska and the spring of Stutz's own soul have become inseparable.
''Chasing Spring" is an eclectic and digressive book. Its author makes the baffling claim that 18,000-foot peaks rise from the deserts of Arizona. He is effusive enough to offer abbreviated ruminations on the Great Salt Lake, the Roman festival of Lupercalia, and the picking of morel mushrooms.
But the charm of ''Chasing Spring" is in its raw enthusiasm, Stutz's personal invigoration braided into the ongoing invigoration of the continent. ''Bring on that juice and joy!" he writes. ''I'm ready now for the spring forest in its mist, spring it its musk, in its spring greens: canopy green, shafts of wild iris green." Reading Stutz is a bit like reading Whitman: You imagine the author stomping gleefully in puddles, peering on his hands and knees into the forget-me-nots and saxifrage.
Spring, of course, means someone is publishing another book about Darwin. Thankfully, this year it's an excellent one. Lyanda Lynn Haupt's ''Pilgrim on the Great Bird Continent" probes Darwin's journals, pocket notebooks, and letters with the goal of understanding how a beetle-obsessed, squeamish, overprivileged 22-year-old could spend five years circumnavigating South America and emerge as a polished naturalist whose vision would change human understanding forever.
Even more than ''Chasing Spring," ''Pilgrim" is about what Haupt calls ''deep watchfulness." She argues that Darwin's notebooks ''foist upon us his strict but beautiful maxim. Nothing in the natural world is beneath our notice -- he almost whacks us on the head with it. Nothing."
Here is a young, apprehensive, occasionally self-absorbed Darwin who gradually strips away his vanities to find an intensity of observation that borders on the religious. He swims with iguanas; he waits four hours on his knees in the mud to glimpse a sedge wren. He stands perfectly motionless in a forest until a shy bird will, in his words, finally ''approach within a few feet, in the most familiar manner." He lies on his back for an entire hour simply to watch the slow circling of condors. Ultimately Haupt's portrait is of a devastatingly sensitive man who teaches himself to approach the world with a profound humility.
Watch what's going on around you, forget being hungry or wet, and bring all your intelligence to being present. If any time of the year is about throwing open your windows and letting the energy of the world pour over you, it has to be springtime.
Perhaps Darwin's own son said it best: ''I used to like to hear him admire the beauty of a flower; it was a kind of gratitude to the flower itself and a personal love for its delicate form and colour. I seem to remember him gently touching a flower he delighted in; it was the same simple admiration that a child might feel."
Anthony Doerr is the author of ''The Shell Collector" and ''About Grace."