But after those days passed, the pronouncements started again. Feeling like Sisyphus watching his boulder roll down the hill yet one more time, I pressed L. on the cancer example.
L. said: "There will always be some expert who will cast doubt on the cancer diagnosis. So long as there is even the possibility of someone with the proper credentials -- or hey, maybe even someone without -- who is to say (with 100 percent certainty) that a homeless person on the street doesn't have an insight that all the so-called experts don't have -- -- , so long as there is this possibility, I say, I will stick to my guns."
I suppose the force of L.'s argument comes down to this: 'To establish that there exists some fact independent of the strongly-held beliefs of group A and B, you first have to establish that fact. But you can never establish any such fact without some doubt casting a mist over our vision of it. If, for example, you assert that AIDS is caused by the HIV virus, who are you to dispute that guy who claims otherwise, even if all the other scientists regard him as having flaked out? You are in even less of a position to dispute him given that before his flake-out interval did work respected by his peers, and even afterwards has done work respected by his peers. And even when you think there is an explanation for the lone scientist going against the vast majority of his peers -- he is taking a risk for a small chance of a potentially huge aggrandizement to his reputation if he turned out to be right, or he is receiving money from the tobacco companies, or from the oil and coal companies -- the fact remains, he has the credentials, so who are you to challenge him? And even if you are yourself the expert in a given field, when a reporter calls your rival after having interviewed you about some issue in our topic of expertise, there is a good chance your rival will say "Don't believe him, he is way out in left field; in fact, he is a total flake; you can count on everything he says being wrong." So doubt will always obscure an alleged fact, meaning that one never completely establishes it. So one never really has access to a fact; all he has access to are beliefs; so if we are going to talk about truth at all, it has to be in terms of beliefs. Since those beliefs vary, truth varies.'