Episode 13: Fabrizio Cariani discusses judgment aggregation
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What is judgment aggregation and why does it matter?
Hello and welcome to Elucidations, a philosophy podcast recorded at the University of Chicago. I'm Matt Teichman.
And I'm Mark Hopwood.
With us today is Fabrizio Cariani, assistant professor of philosophy at Northwestern University, and he's here to talk to us about judgment aggregation. Fabrizio Cariani, welcome.
Thank you. Uh thank you, Matt and Mark.
Well, the question to begin with I think is pretty obvious. Uh what is judgment aggregation?
Judgment aggregation is a formal theory that basically tries to characterize uh various possible ways in which you aggregate individual opinions into collective opinions. It's actually studied by people in all kinds of fields. It's studied by people in economics, political science, and philosophy, and even in artificial intelligence. I've been interested in how you should apply this theory to some questions in epistemology. So questions concerning what could possibly be For a group to have a belief.
So I guess some philosophers maybe think that it is impossible for groups to have beliefs, but I guess y you think that it is the case, that a group of people can believe something as a group, over and above what the individuals in the group believe individually.
So it depends a little bit on what you mean by having a belief and also a little bit on what you mean by over and above. There is one sense in which uh it's clear that it's much harder to say that a group has a belief. And for example, you might think that for something to have a belief it has to have a brain. And if you think that, then well, I guess groups have multiple brains, but they don't have a one brain that's the brain of the group. However, there is another sense of having a belief or another sense that we make of the idea of ascribing beliefs to agents, in which what we do is ascribe beliefs as part of the general enterprise of, for example, explaining actions, understanding in general how intentional agents behave.
If you have this picture, there is as much reason to ascribe belief to a group as there is to ascribe belief to an individual because obviously groups make decisions, obviously they do so on the basis of reasons. And in fact, this morning I actually Googled the expression the committee believed without anything following, and I got well over a million hits. The idea of uh groups of people having belief is actually somewhat entrenched in the way in which we talk. about actions and the way in which we talked about subjects in the broadest sense of the term behaving. Now there was another part of your question which was about whether or not these beliefs are over and above the beliefs of the individuals.
And I think that's a bit delicate and it depends a little bit on what you mean by over and above. Saying that a group has a belief over and above the group of the individual could mean that the group belief is not determined by the beliefs of the individuals. And that's actually something that I don't necessarily believe is true.
How can we understand whether a group can have beliefs of its own?
I think the opinions of the group are in some sense determined by the opinions of the individual, members of the group. But on the other hand, I think it's possible for the opinion of the group to be different from the opinions of any one of the members of the group. So there is a Somewhat subtle distinction there, but it's a distinction you could possibly want to draw. For example, let's give a very simple example. Imagine a condo association that has to decide whether or not the windows in the building have to be cleaned. It could be that there is at precisely 50% split among the people in the condo association as to whether or not the windows should be cleaned. So 50% of the people think the windows should be cleaned, 50% think the window
should not be cleaned, let's say because it's too expensive to clean them up. Now, you may think that the correct opinion to ascribe to the group in that case is something like an indeterminate opinion, something like the group suspends judgment on whether or not the windows should be cleaned.
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Chapters
8 chapters
1
What is judgment aggregation and why does it matter?
0:19–2:58
2
How can we understand whether a group can have beliefs of its own?
2:58–6:04
3
Why can a simple majority rule lead to inconsistent group beliefs?
6:04–8:56
4
What are the main constraints that shape aggregation rules?
8:56–11:00
5
Why is the independence constraint controversial in judgment aggregation?
11:00–14:20
6
How do super‑majority thresholds help avoid logical inconsistencies?
14:20–17:10
7
When should different aggregation principles be applied in practice?
17:10–20:30
8
What open questions remain for the study of group belief formation?
20:30–22:54
Speakers
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