Episode 40: Johan van Benthem discusses logical dynamics
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What is the main topic discussed in this episode?
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What is the traditional view of logic and how does Johan propose to broaden it?
Hello and welcome to Elucidations, a philosophy podcast ordinarily recorded at the University of Chicago, but which today is being brought to you from Amsterdam. With me today is Johan von Bentham, University Professor of Pure and Applied Logic at the University of Amsterdam, and Henry Walgrave Stewart Professor of Philosophy at Stanford University. He is here to talk to us about logical dynamics. Johan von Bentham, welcome.
Indeed. Thank you, Matt, for doing this. I'm uh looking forward to it.
How does the restaurant ordering scenario illustrate information flow and inference?
I guess maybe we can just begin with a discussion about what logic is. What is it that logicians study?
Well, there is the traditional answer uh about uh the object of logic. Then you'd say that logicians study uh valid inferences and maybe highlight it in mathematical proofs. as maybe also the broader conception of logic that I'm interested in as you know, uh for instance in the new book which I've just written, in which I actually try to push the boundary of that definition towards logic as a study of information flow. and everything structured that can be found there.
And one really nifty example you like to give about sharing and exchange of information between people uh has to do with a uh family ordering some dishes at a restaurant. How does that example go?
Yes. It's an example that was actually uh born uh out of pressure because uh I had to give a a lecture about logic to children age around eight. As I was preparing, uh it it actually occurred to me that If I had to think of concrete scenarios where logic plays a role, uh you would actually see various things happening at the same time. Okay, so let's have the scenario. You're in a restaurant with your mother and father, let's say there's three people, and you've each ordered one dish. Let's say there's a fish, meat, and vegetarian. I was actually a bit worried with the children because do they actually go to restaurants? But they do, even at age eight. And okay, now the following happens, and this is something you can really see in restaurants all the time.
Somebody has taken your order, but out of the kitchen comes some new person carrying So What do we see then? So this new person has an informational problem to solve because he needs to hand out the right dish to the right person. And this is actually you know, one can ask. So I ask the children, I ask audiences and we all agree what you're gonna see. The first thing that the waiter is gonna do is ask a question. So for instance he's gonna ask uh who has the fish? When that gets answered, he puts the fish dish and he has two dishes left.
What are the three fundamental informational actions (questions, observation, inference) identified for logical study?
So what we're gonna see is another question, for instance, who has the meat? He puts that dish And then comes of course an interesting moment because he's holding one more dish, but now he just puts that without asking. So to me this is a very natural scenario that belongs together. And an interesting issue for logic is what informational actions have we actually seen here?
A traditional answer to that would be something like once the waiter has learned that, let's say, the mother has the fish and the father has the meat, he can then infer that the child has the vegetarian dish. You know, it's um in virtue of his grasp of principles of good and bad reasoning that he's able to come to this conclusion without asking a third question. Right.
Right. And I totally agree with that. Of course there could be discussion about how conscious this inference actually is, but I would think of that last action as an inference. But to me the scenario has a unity. If I only say that the last part is logic, I actually distort what's taking place because the waiter had only one problem to solve, which was where to put these dishes. And to me, for instance, the question And the answers that we also see in this scenario are equally important logical acts.
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Chapters
8 chapters
1
What is the main topic discussed in this episode?
0:00–0:36
2
What is the traditional view of logic and how does Johan propose to broaden it?
0:36–1:06
3
How does the restaurant ordering scenario illustrate information flow and inference?
1:06–3:15
4
What are the three fundamental informational actions (questions, observation, inference) identified for logical study?
3:15–7:04
5
How does public announcement logic model the change from ignorance to knowledge?
7:04–11:37
6
What are “soft announcements” and why do they add complexity to logical dynamics?
11:37–14:02
7
How can game theory help analyze multi‑step informational interactions?
14:02–18:19
8
What role do miscommunication and its correction play in dynamic logic?
18:19–35:55
Speakers
1 identifiedMore from Elucidations
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