December 20th, 2015
(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: email@example.com
Except sometimes it is. Rationalism guided Einstein toward his theory of relativity, which he believed in wholeheartedly on rational grounds before it was ever tested. “I hold it true that pure thought can grasp reality, as the ancients dreamed,” Einstein said in 1933, years after his theory had been confirmed by observations of starlight bending around the sun.
The question for the philosophers is: Without experiments, is there any way to distinguish between the non-empirical virtues of vortex theory and those of Einstein’s theory? Can we ever really trust a theory on non-empirical grounds?
In discussions on the third afternoon of the workshop, the LMU philosopher Radin Dardashti asserted that Dawid’s philosophy specifically aims to pinpoint which non-empirical arguments should carry weight, allowing scientists to “make an assessment that is not based on simplicity, which is not based on beauty.” Dawidian assessment is meant to be more objective than these measures, Dardashti explained — and more revealing of a theory’s true promise.
Gross said Dawid has “described beautifully” the strategies physicists use “to gain confidence in a speculation, a new idea, a new theory.”
“You mean confidence that it’s true?” asked Peter Achinstein, an 80-year-old philosopher and historian of science at Johns Hopkins University. “Confidence that it’s useful? confidence that …”
“Let’s give an operational definition of confidence: I will continue to work on it,” Gross said.
“That’s pretty low,” Achinstein said.
“Not for science,” Gross said. “That’s the question that matters.”
Kragh pointed out that even Popper saw value in the kind of thinking that motivates string theorists today. Popper called speculation that did not yield testable predictions “metaphysics,” but he considered such activity worthwhile, since it might become testable in the future. This was true of atomic theory, which many 19th-century physicists feared would never be empirically confirmed. “Popper was not a naive Popperian,” Kragh said. “If a theory is not falsifiable,” Kragh said, channeling Popper, “it should not be given up. We have to wait.”
But several workshop participants raised qualms about Bayesian confirmation theory, and about Dawid’s non-empirical arguments in particular.
Visions of Future Physics
Nima Arkani-Hamed is championing a campaign to build the world’s largest particle collider, even as he pursues a new vision of the laws of nature.
In a Multiverse, What Are the Odds?
Testing the multiverse hypothesis requires measuring whether our universe is statistically typical among the infinite variety of universes. But infinity does a number on statistics.
In Fake Universes, Evidence for String Theory
Researchers are demonstrating that, in certain contexts, string theory is the only consistent theory of quantum gravity. Might this make it true?
Carlo Rovelli, a proponent of loop quantum gravity (string theory’s rival) who is based at Aix-Marseille University in France, objected that Bayesian confirmation theory does not allow for an important distinction that exists in science between theories that scientists are certain about and those that are still being tested. The Bayesian “confirmation” that atoms exist is essentially 100 percent, as a result of countless experiments. But Rovelli says that the degree of confirmation of atomic theory shouldn’t even be measured in the same units as that of string theory. String theory is not, say, 10 percent as confirmed as atomic theory; the two have different statuses entirely. “The problem with Dawid’s ‘non-empirical confirmation’ is that it muddles the point,” Rovelli said. “And of course some string theorists are happy of muddling it this way, because they can then say that string theory is ‘confirmed,’ equivocating.”