That post stirred up an in-tray tsunami. A reader writes:
Red herring: “…there doesn’t seem to be any particular logical or metaphysical reason to believe that the universe is as simple as it could be.” I don’t think William of Occam or anybody else says that. For science, the simplest explanation that accounts for all the available data is the best working hypothesis going forward, because it doesn’t clutter the model.
Additional experiments and observations may require an expansion or correction to account for new data, which will then become the new working hypothesis, or they may falsify the old one and require starting over. If you are trying to determine why it grows dark at night, there is no need to bring in a light-dimming sky fairy when the bulk of the earth coming between us and the sun answers the question very well, no matter which is moving.
Copernicus started a scientific revolution by placing the sun at the center of things, thus eliminating the need for deferents and epicycles and all the complicated calculations required by the Ptolemaic system. No one today computes planetary positions and motions by the old methods, except perhaps as an historical exercise, because something new, better, and easier has replaced them.
On the other hand, Kepler’s work was a refinement, not an overthrow, of the Copernican system, based on new data drawn largely from Tycho Brahe’s detailed observations. The long-held Aristotelian idea that heavenly bodies moved in circular orbits because circles represent perfection was discarded in favor of data-imposed ellipses. That became the new simplest hypothesis, and in its turn was further refined to account for perturbations of one planet’s orbit by another’s gravitational field.
Another writes:
In order to explain planetary orbits while clinging to geocentrism, astronomical models showed celestial bodies orbiting in a circle around earth. But in order to account for their places in our sky, there had to be added little orbital semi-circles branching off from the main circular orbit, with orbital semi-circles branching off from the first set of semi-circles, and so on and so on: the end model looked like a big circle surrounded by hundreds of smaller circles surrounded by thousands of even smaller circles surrounded by millions of the tiniest circles. This is where Occam’s Razor was best applied. Do planets really orbit in a ridiculous manner like this, as predicted by geocentrism? Or was it perhaps time to embrace heliocentrism, which did away with the absurd branches of semi-circle orbits.
Another:
Occam’s Razor says is that that in our search for answers, we should pursue the simpler hypotheses first, and only complicate them – “multiply entities” – when necessity arises. It’s a methodological statement, not a veridical one; a statement about how inquiry ought to be conducted, not about the truth-value of its results. Unfortunately, surprising number of people misunderstand what Ockham’s Razor is.
The Dish 