“No Guarantee: Coherence, Rationality, and Fragmentation” - Camilo Martinez (Central European University)
Forthcoming in Thought
Incoherence
Have you ever scheduled two important meetings at the same time? Or maybe you—like me—once believed that Egypt is a Middle Eastern country, that there are no Middle Eastern countries in Africa, and that Egypt is in Africa?
If your answer is “yes,” then you’ve experienced incoherence. Incoherence happens when the contents of our minds—our beliefs, plans, and projects—don’t hang well together. When we’re incoherent, we have inconsistent beliefs, conflicting plans, or irreconcilable projects.
Incoherence is a common condition. We’ve all experienced it at some point—even brilliant philosophers. For example, in his paper “Logic for Equivocators,” David Lewis recalls a time when he held inconsistent opinions. He writes:
“I used to think that Nassau Street [in Princeton, NJ] ran roughly east-west; that the railroad nearby ran roughly north-south; and that the two were roughly parallel (...) So each sentence in an inconsistent triple was true according to my beliefs, but not everything was true according to my beliefs.”
Irrationality
When we’re incoherent, something seems to be wrong with our minds. Indeed, many philosophers think that incoherence is irrational. An incoherent mind falls short of rational standards, so when we catch ourselves having incoherent beliefs, plans, or projects, we should be ready to revise them.
However, while many philosophers agree that incoherence is irrational, they disagree about why.
Structuralists claim that incoherence is irrational because rationality specifically demands that our minds have a coherent structure. Some structuralists even think that coherence is all that rationality ever demands of us. For example, writing about practical reason, David Hume famously declared that it’s “not contrary to reason to prefer the destruction of the whole world to the scratching of my finger” (provided this preference hangs well with my other preferences).
Anti-structuralists, by contrast, deny that rationality specifically demands coherence. They don’t think coherence has any rational value in itself. To put it in the words of Niko Kolodny, it seems outlandish that rationality would require something as trivial as mere “psychic tidiness” just as it requires us to respond to the apparently more meaningful demands of knowledge or friendship.
Guarantee
So how do Anti-structuralists explain what makes incoherence irrational? In two recent books, Errol Lord and Benjamin Kiesewetter independently argue for the following claim: incoherence is irrational because it guarantees failing to respond correctly to one’s reasons.
Consider a toy example: Suppose you believe both that Erwin, the cat, is on the mat and that he’s not on the mat. This combination of beliefs guarantees that you’re failing to respond correctly to your reasons. If you have good reason to believe Erwin is on the mat, then you have good reason not to believe he isn’t there, and vice versa. So, if one of your beliefs is reasonable, the other isn’t.
It’s natural to think that rationality demands that we respond correctly to our reasons—in other words, that we be reasonable. So, if Lord and Kiesewetter are right that incoherence guarantees being unreasonable, then we have an elegant explanation for why incoherence is irrational.
Fragmentation
But Anti-structuralists like Lord and Kiesewetter aren’t right. Or so, at least, I argue in my paper.
To see why, let’s consider a different question: not “why is incoherence irrational?” but “how is incoherence even possible?” Go back to Lewis: how could he, psychologically speaking, believe all the things he believed at the same time? His beliefs were clearly incoherent. It seems like a moment’s reflection should’ve been enough for him to realize this.
Fortunately, Lewis himself offers a diagnosis. In the same paper, he writes:
“My system of beliefs was broken into (overlapping) fragments. Different fragments came into action in different situations, and the whole system of beliefs never manifested itself all at once. The first and second sentences in the inconsistent triple belonged to—were true according to—different fragments; the third belonged to both. The inconsistent conjunction of all three did not belong to, was in no way implied by, and was not true according to, any one fragment.”
Lewis was incoherent because his mind wasn’t unified—it was fragmented (Fig 1). His incoherent beliefs influenced his thinking and acting at different times and in different situations. Hence, they were “quarantined” from each other; he couldn’t appreciate their incoherence.
No Guarantee
Fragmentation is one of the best accounts out there of how incoherence is psychologically possible. In the paper, I argue that this is bad news for Anti-structuralists like Lord and Kiesewetter. This is because, when someone is fragmented, there’s no guarantee that they’re failing to respond correctly to their reasons.
You can find my detailed argument in the paper, but stripped down to its basics the idea is this: when we’re fragmented we don’t have access to all of our information all of the time. Rather, different bits of information are available to us in different situations. Because of this, we might respond impeccably to whatever information is available to us in each situation without being in a position to tell that the totality of our information is inconsistent.
This is what happened to Lewis. He responded correctly to the evidence available to him when he reasoned. He just couldn’t know, while reasoning, that he had conflicting evidence.
Upshot
If I’m right, then Structuralists seem right that rationality specifically demands coherence. Otherwise, we couldn’t explain what goes wrong with people who, like Lewis, end up incoherent because they’re fragmented, since they may still be responding correctly to their available reasons.
Toward the end of my paper, I sketch a defense of Structuralism along these lines. I argue that fragmented beings like us would benefit from coherence demands—not only to respond correctly to their reasons, but also to detect when their evidence is misleading.
If this is right, then coherence isn’t just psychic tidiness after all; it’s a rational necessity for minds like ours.