Take death, which seems a pretty definitive state. “The body is just a lump,” Mr. Alda says. “Life is gone. But if you step back a bit, the body is actually in a transitional phase while it slowly turns into compost — capable of living in another way.”

Frank Wilczek of M.I.T., a Nobel Prize winner in physics, would retire the distinction between mind and matter, a bedrock notion, at least in the West, since the time of Descartes. We know a lot more about matter and atoms now, Dr. Wilczek says, and about the brain. Matter, he says, “can dance in intricate, dynamic patterns; it can exploit environmental resources, to self-organize and export entropy.”

We can teach it to play chess.

But don’t get too excited. Roger Schank, a computer scientist and psychologist for the nonprofit group Engines for Education, says that a chess-playing computer won’t tell us anything about how or why humans play chess nor will it get interested in a new game when it gets bored. We should abolish the term “artificial intelligence,” he says, adding: “There really is no need to create artificial humans anyway. We have enough real ones already.”

Stewart Brand, founder of the “Whole Earth Catalog,” among many things, wants to talk about nuclear power, which he argues has been hampered by the unprovable notion that no level of radiation, no matter how low, is safe. As a result, billions of extra dollars have been spent to provide “meaningless levels of safety” around nuclear power plants — meaningless because our cells contain mechanisms for repairing radiation damage to DNA and because, moreover, “we all die.”

Professor Dawkins and Lisa Feldman Barrett, a psychologist from Northeastern University, both attack the concept of essentialism, which holds that things like dogs and cats, triangles and trees, space and time, emotions and thoughts — all have an underlying essence that makes them what they are. This works great in math, Professor Dawkins argues, but is a disaster when applied to species or politics, disallowing the possibility of change or gradation.

“Florida must go either wholly Republican or wholly Democrat — all 25 Electoral College votes — even though the popular vote is a dead heat,” he complains. (The number is now 29.) “But states should not be seen as essentially red or blue: they are mixtures in various proportions.”

Max Tegmark, a cosmologist at M.I.T., claims we could get along just fine without the notion of infinity. The computer scientist W. Daniel Hillis of the technology company Applied Minds claims we can get along without the notion of cause and effect, which he says is just an artifact of our brains’ penchant for storytelling. Seth Lloyd, a computer scientist at M.I.T., says it’s time to lose the notion of a universe.