ideasthesia

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Ryan Collison

I write about cool science and share it here.

Hierarchical neural architecture with top-down predictions meeting bottom-up errors at every level

The Bayesian Brain: Prediction All the Way Down

Series: The Free Energy Principle | Part: 6 of 11 Your brain is not a camera recording reality. It’s a prediction engine generating reality. Right now, most of what you’re seeing isn’t coming from your eyes—it’s coming from your visual cortex’s best guess about what’

Perception-action loop showing prediction error minimization through both belief updating and world changing

Active Inference: When Perception Becomes Action

Series: The Free Energy Principle | Part: 5 of 11 You’re thirsty. Your body needs water. But “thirst” isn’t just a passive sensation you observe—it’s a prediction error that drives you to act. Your internal model says “I should be hydrated,” your sensory receptors say “you’re

Approximation landscape showing tractable path through intractable probability space

Variational Inference for Humans: The Math Made Intuitive

Series: The Free Energy Principle | Part: 4 of 11 You can’t see what’s actually out there. Your brain is locked in a dark skull, receiving only indirect signals—photons triggering retinal cells, molecules binding to olfactory receptors, pressure waves vibrating cochleas. From this limited, noisy data, you must

Statistical membrane separating internal states from external world—the Markov blanket as identity boundary

Markov Blankets: The Boundaries That Make Things Things

Series: The Free Energy Principle | Part: 3 of 11 Where do you end and the world begins? Point to your skin and you’ve already made assumptions. Skin cells slough off constantly. Bacteria in your gut outnumber your own cells. The oxygen in your blood came from outside. The thoughts

Entropy gradient showing ordered system resisting dissolution into environmental chaos

Surprise Is the Enemy: Why Living Systems Minimize Free Energy

Surprise Is the Enemy: Why Living Systems Minimize Free Energy Series: The Free Energy Principle | Part: 2 of 11 You are, statistically speaking, impossible. Your body temperature hovers within a degree or two of 37°C. Your blood pH stays between 7.35 and 7.45. Sodium and potassium concentrations

Mathematical visualization of free energy minimization—prediction meeting reality across a Markov blanket boundary

The Equation Behind Everything: An Actually Accessible Introduction to the Free Energy Principle

The Equation Behind Everything: An Actually Accessible Introduction to the Free Energy Principle Series: The Free Energy Principle | Part: 1 of 11 In 2006, Karl Friston—a neuroscientist at University College London—published a paper with a claim so audacious it should have been laughed out of the room. He

Swiss Army knife unfolding transformation symbols and category theory morphisms—possibility as fundamental

Constructor Theory

What if physics asked the wrong question? Traditional physics asks: “Given these initial conditions, what happens next?” Constructor theory asks something different: “What transformations are possible, and what makes them possible?” David Deutsch and Chiara Marletto developed constructor theory as a new foundation for physics—one that puts possibility and