There are some big thinkers who respond to this question, but some of the answers involve some lame reasoning.
The first answer given is by cosmologist Andrei Linde, who gives “Uniformity and uniqueness of the universe” as the scientific idea he thinks should be retired. Linde cites cases in which our universe seems to be tailor-made for life, and notes that if the mass of the electron were slightly different, or protons were not almost the same mass as neutrons, or the energy of empty space were not just right, we wouldn't be here. Linde then suggests that we should therefore adopt the concept of a multiverse, a vast ensemble of universes:
If the universe were given to us in one copy..we would need to speculate about the divine cause making the universe custom built for humans. Meanwhile, in the multiverse consisting of many different parts with different properties, the correlation between our properties and the properties of the part of the world where we can live makes perfect sense.
But this reasoning by Linde is not correct. If there are a million billion trillion quadrillion universes, then the match or correlation between our universe and a habitable universe would not make any more sense (and would not be even .0000000001 percent more likely) than it would be if there is only one universe. This in because in both cases the chance of our universe being a habitable universe is exactly the same. Multiplying the number of universes does not change the probability of any one of those universes being successful. It may change the likelihood of at least one of those universes being successful, but it would have no effect at all on the likelihood of any one of those universes being successful. Similarly, selling a million lottery tickets with 7 random digits may increase the chance that some ticket buyer may win, but it does nothing to increase the chance that any one of those tickets will be a winner. To put it in terms of probability mathematics, increasing the number of trials does not increase the chance of any one trial being successful. So if our universe requires an almost miraculous conspiracy of lucky breaks to be habitable, you do nothing to make that seem less miraculous by supposing a vast number of universes. The habitability of our universe (not to be confused with some universe) is a zillion to one shot before the multiverse assumption, and it's just as much of a zillion to one shot after the multiverse assumption.
Another scientist who offers a flawed answer to the Edge.org question is physicist Alan Guth, who answers the question of “What scientific idea is ready for retirement?” by saying: “The Universe Began in a State of Extraordinarily Low Entropy.” In fact, there are still absolutely compelling reasons for believing that the universe did begin in a state of extraordinarily low entropy. According to the second law of thermodynamics, entropy is always increasing. So if we just rewind things back to the time of the Big Bang, we are left with a state of incredibly little entropy. The diagram below illustrates the point:
Why would Guth want to propose that the universe did not begin in an incredibly low entropy state? Because the low entropy of the early universe is a major reason for doubting the cosmic inflation theory that Guth originated (a point that cosmologist Roger Penrose has made). It turns out that the cosmic inflation makes the “incredibly low early entropy” problem much worse, and requires that the universe must begin in an even more special state (entropy-wise) than it would have begun in without cosmic inflation. As physicist Sean Carroll says, "To get inflation to start requires even lower-entropy initial conditions than those implied by the conventional Big Bang model." So naturally Guth wants to bolster his pet theory by getting rid of ultra-low entropy at the Big Bang, somewhat in the same way that a believer in Earth's uniqueness might want to get rid of evidence for extrasolar planets.
But what does Guth propose as a way to get rid of this ultra-low entropy at the universe's beginning? He suggests some theoretical work he describes like this: “This work, by Sean Carroll, Chien-Yao Tseng, and me, is still in the realm of speculation, and has not yet been vetted by the scientific community."
That candid statement shows on what very weak speculative ground Guth is standing on in this matter. Let's stick with the facts, and continue believing that the universe did begin in an astonishingly low entropy state.
Another flawed answer to the Edge.org question is given by Bruce Hood, who answers the question of “What scientific idea is ready for retirement?” by giving this answer: “The self.” Hood gives us some materialist reductionist nonsense that is designed to make you think that you don't have a you. Sorry Bruce, but having read my Descartes long ago, I can paraphrase him by simply saying: “I think, therefore you're wrong.” To anyone who has a self, there is nothing less necessary than disproving an argument against the self (only a computer might need to make such an argument).
Similar comments can be made about the strange, strained reasoning of physicist Nigel Goldenfeld, who suggests “Individuality” as the scientific idea that should be retired, and who assures us that “you can't attribute an event in time to a single earlier cause.”
Another weak answer to the Edge.org question is given by physicist Steve Giddings, who suggests “spacetime” as the scientific idea that should be retired. Giddings points out that general relativity and quantum mechanics need to be reconciled, and that the idea of spacetime may not survive once that happens. Yes, but that may take centuries; and meanwhile we need the notion of spacetime.
Worse than Giddings' answer is the answer given by W. Daniel Hillis, a physicist who suggests “Cause and effect” as the scientific idea that should be retired. He says, “We will come to appreciate that causes and effects do not exist in nature, that they are just convenient creations of our own minds.” Nonsense. If I jump off a high cliff, my jumping will be the cause, and my death will be the effect.
Don't come near this if you're a Hillis fan
Another silly answer is given by Jerry Coyne, who suggests “Free Will” as the scientific idea that should be retired. He claims there is “no evidence for a mind separate from the physical brain,” something that would be doubted by many people studying near-death experiences. Coyne then claims “recent experiments support the idea that our 'decisions' often precede our consciousness of having made them.” These experiments (involving a difference of only an instant) have been well-debunked by detractors (anyone interested can read this article). The supposed evidence for a “decision before the decision” is very dubious, since we don't have the technology to read a mind, and can't tell exactly when a person has made a decision by reading his brain activity.
Another dubious answer is given by philosopher Daniel C. Dennett, who answers "the hard problem of consciousness" as his scientific idea that should be retired. This is the problem of how matter (something so different from consciousness) could give rise to consciousness. I suspect that Dennett wants to get rid of the problem because he has no answer to it, and it is troubling to his worldview. He gives no real reason why the problem should be retired. Dennett's imperfect judgement may be shown by his very misleading statement elsewhere: "We have pretty much figured out how life got started, the big bang, black holes, gravity, and electricity." At least two of these (the big bang and the origin of life) are still very major mysteries, the big bang in particular being completely unexplained.
The home page of Edge.org currently trumpets itself as “a forum for the world's most brilliant minds,” although you would never know it from some of these answers to this year's Edge.org question.
But there were some good answers to the question of what scientific idea should be retired. Among the more intelligent answers (provided by various thinkers) were the following:
There Is No Reality in the Quantum World
M Theory/String Theory is the Only Game in Town
Only “Scientists” Can Do Science
Natural Selection is the Only Engine of Evolution
Unlimited and Eternal Growth
Unbridled Scientific and Technological Optimism
Science Makes Philosophy Obsolete
The Atheism Prerequisite
The Mind Is Just the Brain
I agree that these ideas are ripe for retirement.