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Theories and metatheories

Posted April 16th, 2009 in Science. Tags: , , , .

I’ve previously called evolution and the Big Bang “theories” to confront widespread confusion regarding the differences between theories and hypotheses. However, using the word “theory” in these instances might be a subtle mistake. It may even be partially responsible for the systemic communications barrier between scientists and the general public.

The central problem is that scientific theories have to make unique, falsifiable predictions. For example, Newton’s theory of motion predicted the locations of the planets with only a single “adjustable” parameter. The Big Bang and evolution are more malleable than Newton’s theory of motion because of the myriad unknown parameters on which they depend.

Tim Thompson calls Big Bang cosmology a metatheory, which has the same relationship to theory as metaphysics does to physics. In other words, metatheories are generic frameworks that contain many different scientific theories. The Big Bang metatheory can (loosely) be defined as “the universe is expanding, so it was smaller, denser and hotter in the past.” Many theories have been proposed and abandoned within this framework. For example, early models couldn’t account for the horizon problem so they were modified by inflation (which would’ve been abandoned if WMAP hadn’t found anisotropies in the cosmic microwave background radiation at the 10-5 level.) Furthermore, WMAP’s discovery of dark energy has ruled out many specific Big Bang theories.

A metatheory has to be specific enough that it can be falsified entirely, though, otherwise it’s not scientific. The Big Bang metatheory could be proven wrong by observations of galaxies that substantially deviate from Hubble’s law. A helium-4 abundance much less than 25% couldn’t be consistent with the Big Bang metatheory, etc.

I think it’s also true to call evolution a metatheory which says something like “all life on earth is descended from a common ancestor(s); observed variations between different species are due to mutations and natural selection.” Darwin’s early model within the metatheory of evolution was extremely simplistic. He didn’t rule out Lamarckian inheritance, so in the strictest sense his theory was falsified in the 1940s by the modern evolutionary synthesis with Mendelian genetics. In the 1970s, punctuated equilibrium revised the existing view that speciation rates were largely determined by mutation rates (and therefore constant in time) by proposing that selection pressures due to migration events or environmental changes also play a significant role. Dawkins’ continuously variable speedism seems like the most accurate viewpoint to me regarding this debate. Evolution can also be falsified entirely, as I’ve noted.

Similarly, germ theory probably qualifies as a metatheory: “microorganisms are the cause of many diseases.” This metatheory has a rich history, introduced ~1000 BCE in ancient Hindu texts, debated by famous Persian scientists ~1000 CE, and more recently demonstrated by Louis Pasteur in the 1860s.

Modern medicine couldn’t exist without this metatheory, but the earliest germ theories probably asserted that all diseases were caused by microorganisms. That’s patently false: some cancers and genetic ailments aren’t contagious at all because their origins are completely different. Not to mention the fact that viruses (arguably) don’t qualify as living organisms. But discrediting the germ metatheory would require showing that microorganisms aren’t responsible for diseases such as cholera that are commonly attributed to them. For instance, these vectors could be an innocent by-product of miasms. (Let me stress that there is no evidence at present to support such a notion.)

Last modified February 6th, 2012
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