Mechanisms Rule Hypotheses Out, But Not In
If there is no plausible mechanism by which a scientific hypothesis could be true, then it’s almost certainly false.
But if there is a plausible mechanism for a hypothesis, then that only provides weak evidence that it’s true.
An example of the former:
Astrology teaches that the positions of planets in the sky when you’re born can affect your life trajectory. If that were true, it would contradict well-established facts in physics and astronomy. Nobody has ever observed a physical mechanism by which astrology could be true.
An example of the latter:
A 2023 study found an association between autism and diet soda consumption during pregnancy. The authors’ proposed mechanism is that aspartame (an artificial sweetener found in diet soda) metabolizes into aspartic acid, which has been shown to cause neurological problems in mice. Nonetheless, even though there is a proposed mechanism, I don’t really care and I’m pretty sure diet soda doesn’t cause autism. (For a more thorough take on the diet soda <> autism thing, I will refer you to Grug, who is much smarter than me.)