Anecdotes can be weak evidence We all know that a lot of people overvalue their N=1 self-study: “I started eating only meat and my arthritis was cured!” Unfortunately, the weakness of this data is often attributed to the fact that it is an anecdote, and so, anecdotes are wrongly vilified as “the bottom of the evidential hierarchy.” In the case of a diet change, the remission of arthritis could be due to any number of reasons: time (perhaps it would have healed on its own, diet change or not), perhaps the person had a reduction in stress leading to lower inflammation, perhaps the person acquired a higher pain tolerance, perhaps the person even lied. Anecdotes can be strong evidence Anecdotes can actually be incredibly strong evidence, and Bayes Theorem tells us as much. An anecdote is strong evidence for a reasonable hypothesis when there is no alternative reasonable hypothesis. That said, sometimes, the apparent lack of alternative reasonable hypotheses is due to one’s lack of knowledge or imagination. I try to counter this, to some degree, by coming up with a mechanistic hypothesis. A gross example (I apologise) For example, I recently heard that armpit odour is caused by bacteria. Bacteria can be killed if exposed to an environment that strongly deviates from the one in which they thrive. So, I scrubbed my armpits with concentrated vinegar, which is acidic (I read that armpit bacteria are basic). I smelled like a salad, so took a shower, and my underarm odour–which I’d had for over a decade–was entirely gone. Even at this point, I was extremely confident that, even if I got the mechanism wrong, this remedy worked. Why the confidence off of so little evidence? Well, what are the chances that the smell just happened to go away on its own, right at that exact moment? Basically zero. Are there any other reasonable causes for the smell to disappear at the exact moment I used the vinegar. Not that I can think of. Why would anything else have been the cause now, but