Ask A Genius 1446: Dynamic Epistemic Logic, Modal Reasoning, and Neuroplasticity
Author(s): Rick Rosner and Scott Douglas Jacobsen
Publication (Outlet/Website): Ask A Genius
Publication Date (yyyy/mm/dd): 2025/07/13
Scott Douglas Jacobsen and Rick Rosner explore dynamic epistemic logic, modal logic, and neurocognitive models of thought. They examine how knowledge updates affect reality models, the brain’s balancing act between stability and plasticity, and logic systems like Kleene’s and von Neumann’s. The conversation bridges philosophy, neuroscience, and computational reasoning.
Scott Douglas Jacobsen: This next topic is primarily empirical—Dynamic Epistemic Logic. It is not about beliefs about beliefs, but about how knowledge updates change models over time. As information increases, so does the accuracy of the model. In a person, this represents a rational agent—someone who updates their internal model of the world based on new information.
Rick Rosner: People’s brains work differently. If you are frequently in an altered state, you might experience effects resembling psychosis. If your brain struggles to form stable categories or object constancies that help interpret your surroundings, you can lose your grip on reality. That is one lens through which to understand schizophrenia—impaired cognitive coherence and disrupted pattern recognition.
Psychoactive drugs can disrupt this, too. Some substances interfere with forming a consistent, moment-to-moment picture of the world. LSD, for instance, affects serotonin receptors and can distort sensory perception, which some find disorienting.
However, a model of reality that’s too consistent can also be limiting—too rigid to allow learning, adaptation, or belief revision.
The brain evolved to balance stability and plasticity. You need a stable representation of the world, but you must also revise it as reality shifts.
Jacobsen: Where does the ability to think new thoughts come from?
Rosner: It likely stems from the structure and dynamics of dendritic connections. The connectome—the network of synaptic wiring—shapes thought patterns and how categories form. It underlies your model of the world.
However, other mechanisms may be involved. We discussed astrocytes last week—glial cells once considered passive support structures. Now, research suggests they may play roles in modulating synaptic transmission and possibly even information processing.
The brain relies on stable yet adaptable architectures. You need a logic system capable of describing that interaction.
You also generate short-term thoughts rapidly, working memory or transient representations. This likely involves neural circuits in the prefrontal cortex and relies on fast neurochemical dynamics. It differs from long-term memory storage, which involves structural changes and consolidation.
Jacobsen: Modal Logic—the logic of necessity and possibility. Thoughts?
Rosner: All this logic discussion reminds me of cooking shows—same basic elements, rearranged. The core goal is avoiding contradiction. It is like quantum mechanics.
Jacobsen: Or information theory. In modal logic, necessity means proposition p is valid in all possible worlds accessible from the current world. Possibility means p is true in at least one accessible world. The key difference is that possibility assumes p is true in some world—an existential claim. What exactly are we thinking? It is an Information Cosmology assumption. If we take the existence of a “current” world—our point of reference—then possibility means p is true in at least one accessible world, and necessity means p is valid in all accessible worlds. This assumption—that there is a current world to begin with—is foundational to how modal logic functions. So IC is compatible with…
Rosner: Think of it as a possibility cone. In the present, you have more certainty than about any past or future moment. The further into the past, the more possible paths could have led here. The further into the future, the more branches diverge.
Jacobsen: We are still on modal logic. Next is Kleene’s three-valued logic. It introduces a third truth value: undefined or indeterminate. This is used in systems where not all propositions can be evaluated as strictly true or false, such as in partial functions or specific computational contexts. John von Neumann had a variation with values like true, false, meaningless, and probable, right?
Rosner: Yes—he explored multi-valued logic systems, especially in the context of quantum logic and computing. Some of his proposals incorporated probabilistic truth values or distinctions between determinacy and indeterminacy.
Jacobsen: Thank you for your time tonight.
Rosner: Talk to you tomorrow.
Jacobsen: Same time-ish.
Rosner: Bye.
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