> "(1) that the supposed effect is really the cause, or in this case that incipient cancer, or a pre-cancerous condition with chronic inflammation, is a factor in inducing the smoking of cigarettes, or (2) that cigarette smoking and lung cancer, though not mutually causative, are both influenced by a common cause, in this case the individual genotype."
> If you think that’s the stupidest thing you’ve ever heard, you can take it up with Sir Ronald Fisher, who actually made this argument with apparent sincerity in a 1957 letter to the British Medical Journal. I mention this in case you didn’t already know what an ass he was.
Of course, it's very possible that there's a common cause. For example, people who are very depressed may choose to smoke, and depression may also cause cancer. I'm not saying it does, I'm just saying it's clearly a possibility that needs experiments to disprove.
The author's claim is so wrong, and yet he seems to genuinely believe it.