changing priors, changing life

I taught a a class last term called Philosophy and Literature, and for our last book we read Plato at the Googleplex, by Rebecca Newberger Goldstein (hereafter RNG). The chapter that gives the book its title is a delightful imitation Platonic dialogue by RNG in which Plato, on book tour, comes to give a talk at Google headquarters. The primary character in the dialogue, aside from Plato himself, is a publicist named Cheryl, a shepherd and minder of authors on tour, who finds herself pushed by Plato to rethink some of her core assumptions about life. The whole conversation is handled with great subtlety and skill – it’s just the kind of thing that I wish I had written, though I have neither the knowledge nor the skill to do what RNG does here.

There’s a point near the end of the dialogue where Cheryl is reflecting on her experience with Plato, and tells a friend that the world needs more people like Plato, “super-arguers” she calls them, because the super-arguer has the power to force us out of our well-worn tracks of thought and practice. As we were discussing this passage in class, I suggested that what Cheryl is saying could be explained in Bayesian terms. So I gave my students a brief overview of Bayesian reasoning. We talked about priors, that is, our current assessments of probability, and how Bayes articulates the ways we revise our priors in light of subsequent experience. The thing that makes Bayesian reasoning so attractive is his ability to see probability not as a fixed proportion, but rather as one that is continually being revised — or at least should be if our minds are functioning properly.

One of the books that we read earlier in the class is Philip K Dick’s The Three Stigmata of Palmer Eldritch — about which I recently wrote a few words here — so I asked my students to engage in a thought experiment: You are walking across campus and see a spacecraft descend and land; from it emerges a man with a mechanical arm, steel teeth, and a kind of visor where his eyes should be, who offers you a drug called Chew-Z, which he claims will confer immortality upon its user. I asked: Would you take the drug? 

My students all agreed they would not. Their priors tell them that such an experience might be an illusion of some kind, or a prank, a reaction to medicine, a side effect of exhaustion – all of these seem clearly more probable occurrences than the actual arrival of a strange man in a spaceship bearing a drug that supposedly confers immortality. And this is setting aside the question of whether, assuming the reality of Palmer Eldritch, his intentions are indeed benign and his claims truthful. But then, I said, suppose it happens again tomorrow, and the day after. Or suppose it happens to a friend of yours, and that friend decides to take the drug and claims to have achieved enlightenment as a result. None of this might be enough to cause you to change your mind about taking the drug, but it would be enough, I think, to cause you to revise your prior assumptions about the possibility of weird men in spaceships landing in Waco. You don’t move from a “confidence interval” of 0% to 100%, but the probability definitely rises. 

So that’s how Bayesian reasoning works. And you can see that what Cheryl is praising in super-arguers like Plato is their ability to cause us to revise our priors. They are, and this is RNG’s chief point in the dialogue, socially useful as, shall we say, gadflies – gadflies who are annoying enough to force us out of our usual patterns. And I think this is true. But, as the example of Dick’s novel suggests, there are other forces in addition to skilled argumentation that can press us to revise our priors. In fact, this is one of the ways in which some scholars have accounted for, or at least helped to explain, the extraordinary effects of LSD upon people: psychotropic drugs have the effect of weakening our priors and making us open to possibilities that we previously had not been open to. Now, as I pointed out, this weakening of our priors may be truth-conducive or may be the opposite: it all depends on how good our priors were. Opening our minds to new possibilities can sometimes lead to disaster, even if it can also sometimes lead to enlightenment.

I also noted that the book we read just before Plato at the Googleplex, Iris Murdoch’s novel The Good Apprentice, concerns some of the same themes. In one sense the story can be described as a retelling of the parable of the prodigal son: we have a father, or rather two potential fathers, and two sons, one who pursues goodness in a way that seems extreme and weird to other characters, and a second who falls into a pit of anguish and despair because — here come the drugs again — he surreptitiously administered a dose of LSD to a friend of his who then walked out of the window of his apartment and fell to his death. So you can see the story as the story of fathers, sons, brothers — a small unit of men who need to find some way to be reconciled to one another.

But that’s not all that the story is about. It seems to me that Murdoch is actually slightly more interested in the effects that extremity of experience or belief have, not upon the people who hold these extreme beliefs or have these extreme experiences, but on the people around them. The younger son Edward’s overwhelming misery is not just a challenge for him, it’s a challenge for everybody who knows him. It forces them to think about guilt and responsibility, about the conditions of healing, about what can be done to atone for sin. They don’t know what to say to Edward, and that reveals to them what they don’t understand about their own lives. Similarly, Stuart, the elder brother, who has commenced a quest for pure goodness and is willing to renounce anything in life that interferes with that pursuit, strikes many of the people in the novel as simply inhuman. He is often compared to an animal, which is odd, because what he is doing is precisely the opposite of animal life: he is questioning his instincts, questioning his desires — but his friends and family don’t have a language for someone who does this. They perceive it to be inhuman, and the only form of inhumanity that they can readily lay hold of is the bestial. In fact, though, Stuart is trying to be a saint. That doesn’t mean he’s right cut: George Orwell once said that “sainthood is a thing that human beings must avoid.” But that’s the proper description for his quest.

In any case, Murdoch’s chief theme seems to be that extremity of moral experience, whether it is an extremity of the desire for good or an extremity of guilt and shame, dislocates lives — not just the lives of the people who are having those experiences but also the lives of those who surround them. And that too can be explained in Bayesian terms: in the presence of moral extremity, everyone’s priors are weakened and disrupted. And in the presence of religious ecstasy. And in the presence of psychotropic drugs. And in the presence of super-arguers. 

So it turns out that what we were dealing with in that class was a series of stories about forces strong enough to weaken our priors. Because when our priors are weakened is when reflection begins. 


Archaic Torso of Apollo
Rainer Maria Rilke (translated by Stephen Mitchell)  
 

We cannot know his legendary head
with eyes like ripening fruit. And yet his torso
is still suffused with brilliance from inside,
like a lamp, in which his gaze, now turned to low,

gleams in all its power. Otherwise
the curved breast could not dazzle you so, nor could
a smile run through the placid hips and thighs
to that dark center where procreation flared.

Otherwise this stone would seem defaced
beneath the translucent cascade of the shoulders
and would not glisten like a wild beast’s fur:

would not, from all the borders of itself,
burst like a star: for here there is no place
that does not see you. You must change your life.

May 14, 2021

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