I. Dreams of Vaccines
The other day, I was speaking with someone I'll call Steve. I will generously describe Steve as skeptical of mRNA vaccines, believing them to be dangerous and possibly part of a grand conspiracy to profit from the deaths of millions. I ask why he believes this and he cites a widely circulated video with someone talking about how dangerous new mRNA technology may be. I haven't heard of this person before but a quick search reveals that, unsurprisingly, they aren't an immunologist: they practice something I've never heard of called "osteopathy." A few more searches reveal this to be a practice that is, at best, a form of alternative medicine whose benefits largely remain empirically undemonstrated and, at worst, complete woo. Furthermore, this person has been a vocal proponent of a certain debunked claim regarding autism and vaccines.
At this point, I am sufficiently convinced that no medical claims this person makes should be taken seriously. I tell Steve as much and show him what I found. He accuses me of ad hominem and that it is my intellectual responsibility to engage with the speaker's argument seriously, to refute the speaker's points.
While the nature of Steve's claim is correct, I think this may be a teachable moment for practical epistemic rationality. I think ad hominem, bulverism, argument from authority, and similar invalid species of argument have a tight grip on ordinary thinking because, though not valid by any means, they are decent heuristics for distinguishing possibly-maybe-true things from complete horseshit.
II. The Demonic Ratio
Suppose I'm riding on the bus when a demon apparates next to me and presses an unsettling, tentacled contraption to my forehead. He wants information regarding the nature of the ratio for an arbitrary circle, assuring me that a wrong answer will result in unspeakable agony for all eternity.
If I knew anything about math before, I certainly don't right now, so I frantically consult the people sitting nearby and get three competing assertions:
- Alice is a research mathematician and she asserts that the ratio of a circle's circumference to its diameter is always the irrational number , which is slightly bigger than 3.
- Bob is a programmer and he asserts that this ratio is always 3.14.
- Charles is the local tie dye enthusiast and he asserts that the question can't be answered because " is infinite."
Alice is a mathematician, maybe she's right? Then again, Bob deals with numbers directly every day in a way that Alice doesn't (she's a geometric topologist), maybe he's right? Charles smells kind of weird, but sometimes smart people smell weird, what about him? His claim is pretty strong and very different from the other two, surely he wouldn't assert something like this without strong evidence. In fact, he immediately offers a response to every question I ask and posits an entire theory on the relationship between sacred geometry, crystal healing, aliens, and why "the man" (he glances at Alice) is suppressing this knowledge.
Clearly the stress is getting to me; this guy's nuts and I really shouldn't take anything he says seriously. I tell the demon as much.
Is̋̆n͚'́t ṱ̡̩͐͒h̗̣̯̒̍͂͠a̤͙̾ͥ͟ţ̎̊̍ ͙͉͙ b̸u͡lver̙̐i̬̼̐̆s̱͈̅̆̊ͅm͟ ?̷
Yes, but unlike Charles, I have concerns that aren't at the bottom of a bong and any heuristic that helps me get to the right answer quickly is literally saving my soul. At least most of the people surveyed agree that the number should be finite!
Ảͭͦͤ̀r̊g̾u͕̤̹̳̖̗̺m̺ȇ̖̞͒n̩̠͌̀tu̯m̾͒̓͋ͨͪͣ ad̘̦̺͍̝ ͛̈́̔̚ p͓̰ö̯̭̜̜́̅͗̏pu͍̞̣̲lum̯͖͂̚
He can't even string together a coherent thought, how can he be right about this?!
F͎͍͊̾̕uͦ̎n͓̹͍da̔̇m̫̣̓͋e̠̱͛̃ṇ̵t̑́ͥ͡a͇l̇ͮ̋ a̖̙͒̔t̞̗͖tr̸i̅͒b̸̼̗͍̏̊͆utiͥ͊on̈͛͆ ͈̱̝͊ͪ̍ ẹ̘̇ͥrr̞̩͍õ͍̗̝̌̅r͆͏̜
I literally saw him light up before you appeared!
P̏o̭̊i͏̬̭ͅs̴on͑͌ȋn͆͊͠g t̟͋he̖͋ ̚ w̝͕el͂̋l̗̊
I remember that I only need to give the right answer, not convince the demon, and so I ignore the slithering horror and turn again to the very concerned-looking Alice and Bob. Alice has spent 10+ years of her life becoming an expert in formal objects that are substantially more complex than circles and she asserts that there are several proofs showing that the value is irrational. When asked why Bob posited a rational number, she says he is a bit confused; his answer represents the first few digits of an infinitely long decimal expansion (and the nature of Charles' confusion becomes more clear); one can get arbitrarily good approximations by truncating this expansion further to the right. When asked for a rebuttal, Bob grumbles that for all intents and purposes it's basically 3.14. I guess he doesn't see the Eldritch horror slithering against my head because he instead glares at Alice and harrumphs something about ivory towers. I realize that he's not overly concerned with precise truth (and possibly a bit sexist). I share this with the demon and say that Bob is probably wrong.
Thͪͧats̴̞̣͍ ȃ̆͏̞͓d̨ ̨ h̀ͨ̚o͎̖m̖̅i̭͎͚n̻e̛͌m̐̋ͦ
Yes, but he's too busy protecting his ego to engage with me seriously. Given her expertise, I will go with Alice's answer.
A͌͋rg̸̈́ű͓̞͈̂̋m̹̥̖e̤̩n̵̟͈͒̒t̛ fr̝͜ỏ̦̻ͮm a̘̥̲ͨͨ͐͜ụ͎̍ͥt̶̯̏h̢o̱͔̓͗r̸i̲t͉y
But she's the only one that engaged her opponents reasonably and explained why they are wrong!
R͂e̢ḁ̪͈̎͂̔͡ll̖̠̒̉͝y͍ b̺̹̪̾͗̄r̰̮̗̫͇̟o̥͚͓ ? b̡u͍̎lv̗̤̗͡eris̝̘m ag͚aȋ̹n͙̠̙ ?
Look man, I'm in no state to rederive this result myself in the ten seconds I have before you get bored and erradicate my soul from all planes of existence. I can't come up with a sufficiently good reason to be convinced of Alice's answer in this time frame, so I'm going to stake everything on the appearance of reasonableness.
I͚̼͇̰̫šn't͐ͬ̚ ťhat a̯̰̝̜̤ b̐ͬ̃ͮád̮̖̝ w̮̟ͣ̑a̻̝̬͓̩̋̍͆̔ͧͩͅy̗ to̖͓ dͩͮͧet͗e̝̝̎̐r͆ͣmͯ̓iǹ͚̦̳ͮ̉ĕ̒̂ͨ w̱͕̰̺̥̼h̰̦̪ͦ͑̔at̗̜̓̚'s T̻̗̳͕̝R̦̪̻̫̘U̼ͥE̞̗̭̻͑̒̐ͪ ?
Only if I'm maintaining the mutually exclusive goals of "get some idea of what the answer ought to be" and "verify the truth to the fullest possible extent." I can't have anything resembling thorough knowledge on all subjects. Over the course of my life, I can at best hope to understand one topic at research level, maybe two if I were Wittgenstein-level brilliant. I can keep refining my views and increasing my understanding, but at the end of the day I can't investigate every claim nor can I become an expert at everything I need to know to have a coherent vision of the world! Given any true statement I can make, there're innumerably many false ones; I can't come to a correct answer by taking all claims seriously! I need to whittle the search space down with hurdles that can separate hypotheses from assertions. Besides, if I were capable of being perfectly rational at all times, I wouldn't be terrified right now because you're more likely to be a hallucination than an actual demon!
A few seconds later the creature melted away and I realized I had been shouting. Alice, Bob, and most of the other passengers are either conspicuously turned away or openly gaping... except for Charles, Charles seems very relaxed as he says:
"You sure told him! What a creepy dude..."
III. When are invalid arguments irrational?
The irrationality of ad hominem is contested in situations where the character or qualifications of the accused are relevant. It would certainly seem unreasonable to dismiss allegations of sexual assault against a sitting president on the grounds that they constitute ad hominem or poisoning-of-the-well; after all, the character of a national leader is (supposedly) pretty damn important. Similarly, if you are bringing an argument that amounts to "This medical authority says mRNA vaccines are dangerous for these reasons," then there is a hierarchy of claims and they are to be investigated in order:
- This person is an authority
- They believe mRNA vaccines are dangerous because...
That they are not trained in the relevant field is evidence against point 1. Being a medical expert is a lot of work and the difference between experts in different subfields is dramatic; I wouldn't trust a podiatrist with my brain surgery as there's going to be little transferable knowledge between feet and brains. That this person holds fringe views on vaccines in general is another point against them, they are holding out against actual authorities in the field. Were this person correct, it would mean that one of the two is true
- The majority of the relevant portion of the medical establishment missed something that was bloody obvious.
- There is a massive conspiracy and all the doctors are in on it.
If you have to assume that a large number of highly credentialed people are absolute morons, then your argument is probably wrong. Likewise, it is fairly easy to do away with conspiracies by interrogating whether there is any limit to their power (see reason 12 here) to say nothing of the reasonable assumption that most people who become doctors and medical scientists probably want to help people, otherwise, they could've harnessed their indifference for human life to make way more money as corporate lawyers. There isn't a likely world where this person is right.
At this point, I might even risk poisoning-the-well by pointing out that this person is extremely motivated to rail against the mRNA vaccine even if they know it's safe. Should they fail to tow the antivaxx line, they will be abandoned by a community they would otherwise continue to profit from in the form of speaking engagements, book purchases, and YouTube ad revenue. Having positioned themselves as a scientific authority that holds an unscientific position for so long, they can't reasonably expect to re-integrate into the ordinary scientific community as a reformed crank; they will be ruined.
None of these refute or even address points 2 through whatever, but do categorically reject 1 whose truth is the only basis on which it is sensible to proceed to investigating 2. In this situation, attacking the (wo)man is not the same as ad hominem, rather, it constitutes a perfectly reasonable dismissal of the argument. In what other situations might something like this be true?
Looking at bulverism again, suppose I am arguing with a misogynist who claims women are intellectually and morally inferior to men and therefore, for the good of society, must remain housebound and subservient to their fathers and husbands as has been done traditionally. To what extent ought I to engage his position seriously? I could talk about how women tend to do better in school, how men tend to engage in anti-social or sociopathic behavior more frequently than women, and so on, but why legitimize the position at all? At risk of bulverism, I can explain how my opponent's position came to be in the first place and that it's origin casts significant doubt on its validity:
My opponent's position is well-explained by centuries of motivated arguments and historical accident. Women, being typically smaller and weaker than men, have historically been subjugated by them and denied any form of political power or intellectual attainment unrelated to domestic affairs. After all, if taught to think critically, they may question their lot in life and work against their fathers, husbands, and other benefactors of what is effectively a system of cheap domestic labor and normalized sexual slavery. The masters in this system have every incentive to create and spread various genera of the "Women are more/less X than men" meme, as it perpetuates a status quo in which they benefit. Meanwhile, women who are intelligent enough to ascertain the true nature of their relationship with men in these times seem likely to either develop depression or stress-related neuroses (seemingly validating the "Women are irrational / hysterical / emotional" memes), to adapt to their niche and focus on things that will help improve their situation (seemingly validating the "Women are virginal / whorish / superficial / small-minded." memes), or some combination of these. It would not be adaptive for women in these times to be political, outspoken, unconcerned with their appearance, or disinterested in domestic life, so we should not be surprised that they historically haven't been any of these.
In the above, the misogynist is claiming that a universal quality is held by all or nearly all women; I am claiming that the misogynist's position is easily explained as a product of well-known aspects of human behavior extrapolated over a well-known power imbalance stretching over thousands of years. I've assumed my opponent is wrong and crafted an explanation as to how their wrong view came about as a result of historical accident, classic bulverism, except my explanation of my opponent's position seems far more convincing than my opponent's thesis, I shouldn't have to work as hard to support my claim as he does for his. Why properly engage the argument when my bulverism is more convincing than his position?
I may be pushing it a little bit on that last example, but I really do think that the rational response of a neutral third party watching us shouldn't be "I reject the anti-misogynist argument on grounds of bulverism;" it should tickle a tiny part of their brain that's checking for some minimal threshold of credibility. There are, of course, limitations to this: I haven't dismantled or even engaged my opponent's argument and relying too much on these heuristics is a good way to keep one's views tribal. But I think it's safe to say that in order for an assertion to be worth my time, it needs to pass some threshold of "seems legit." Indeed, there are far more false claims about the world than there are true ones so a claim is not, on its own, worthy of anything other than outright dismissal. If I can immediately conjure a convincing sounding explanation for your view after negating it, then you're going to need to work a little harder. If you're appealling to non-authorities (or are a non-authority), then you can't feel put out because I'm giving you short shrift, I'm going to do the efficient thing and pay attention to people who are more likely to be right.