Knowledge, according to a metaphor invented by Otto Neurath and made famous by the philosopher WVO Quine, is a boat that must be repaired at sea. "Where a beam is taken away a new one must at once be put there," Quine wrote, "and for this the rest of the ship is used as support. In this way, by using the old beams and driftwood, the ship can be shaped entirely anew, but only by gradual reconstruction." One can't replace the hull at a stroke, in other words, and one can't change one's mind about everything all at once.
Last Thursday a certain storm-battered vessel received some unexpected reinforcement. Richard Muller is an astrophysicist at UC Berkeley; he also has a reputation for being a climate-change sceptic and something of an intellectual buccaneer. All these qualifications must have made him an attractive candidate to lead the Berkeley Earth Surface Temperature study, a survey of the data on global temperature trends.
The project was intended to settle the argument over whether the Earth is actually getting warmer. It was partly funded by the billionaire anti-warming propagandists the Koch brothers, and received the co-operation of Anthony Watts, a former TV weatherman whose blog has co-ordinated some of the most energetic and detailed rebuttals of official research methods. Muller had commented favourably on Watts, critically on what might be called the climate science establishment, and was generally agreed to stand outside the latter. Nevertheless, his provisional findings, announced at the end of March in the US House of Representatives, pointed to an average temperature increase of 0.7 degrees Celsius since 1957.
Muller called the result "unexpected", which is a bit rich seeing that it merely corroborated the reports produced by the UK Hadley Centre, the US National Oceanic and Atmospheric Administration, and Nasa. He also affirmed that the existing body of world temperature data "has sufficient integrity to be used to determine temperature trends", a point that will have enraged Anthony Watts, who insists that too many weather stations are situated in built-up areas for their measurements to be reliable.
It will be a couple of months before Muller's team conclude their research. It will be a lot longer before the most committed sceptics (odd that this phrase no longer registers as a contradiction) accept their verdict, assuming Muller doesn't pull another volte-face before publishing.
Indeed, Muller is unusual in the climate field for having apparently changed his mind about something. He checked the data and was surprised to find it stood up. Most of the rest of us can be divided into immovable factions, and debaters on either side of the question often despair at the presumed irrationality or dishonesty of their opponents.
Of course, it is possible that either or both sides are entirely stupid or corrupt. But it is also possible that they aren't; that both are sincere seekers after truth, using the methods sanctioned by their peers and internalised as the dictates of common sense. For large questions, where it isn't only a single point of fact that is in doubt but an entire system of authority and implicit trust, shifting one's opinion may feel like trying to make a new ship from scratch, out on the open water.
This is a charitable analysis - too charitable, perhaps - but it isn't a cheerful one. What can you say to persuade someone who doesn't share your premises? In the case of climate change, the question is not idle: if the scientific consensus is correct, millions could find themselves at sea in a miserably non-figurative sense.
For myself, I respect mainstream science. I found the Stern report convincing insofar as I could judge it, and was unpersuaded by the suggestions of foul play at the University of East Anglia. I'm a warmist, to use the pejorative term, and perhaps that means there's no hope for me. Nevertheless, I welcome Muller aboard our boat, and am optimistic that his story will convince others that they don't have to rebuild the whole damn thing themselves.
