It’s amazing how much stuff you can know is untrue or extremely unlikely by understanding that there is no mechanism by which it could occur. That’s part of why certain conclusions (which I usually get right) seem so obvious to me while others miss them. To achieve this, I always ask myself, “What is the mechanism by which that could occur?”

If there is none, or a highly unlikely or speculative one, I can be fairly certain that what the person is claiming is untrue.

For instance, claims about Covid-19 destroying the immune system. I asked myself, “What is the mechanism by which that could occur in a normal human immune system?” I couldn’t think of one given how coronaviruses work (and Covid-19 is a fairly normal CV). Thus I concluded this claim was likely false. Of course it depends on having a good amount of background knowledge, but even without that my method can work fairly well.

When I see some claim I always ask, “What’s the possible mechanism in the world by which that could be the case?” If there isn’t one I either reject the claim or investigate it far more if I think I am missing something (sometimes that happens too).