Idea
Predict the spread instead of the next step
You may not know which way a suspended particle will move next. You can still ask how a population of such particles spreads over time. A probability distribution describes which outcomes are more likely and how widely they vary.
Brownian motion is an example. Albert Einstein related the irregular movement of small suspended particles to molecular activity and derived testable statistical relationships. The visible motion provided evidence about molecules too small to see.
An unpredictable path can belong to a predictable distribution.
Ask what the model promises to predict before judging its accuracy.
Where it breaks down
A probability model can be wrong. A deterministic system can also be hard to predict if its starting conditions are uncertain. Difficulty predicting something does not, by itself, make it stochastic.
How it connects
Statistical predictions turn irregular paths into measurable expectations.
This idea appeared in Predictable patterns without predictable paths, the Involves connection for October 20, 2026, which asked: Can randomness produce something we can reliably calculate?
Check yourself
Can a deterministic system be difficult to predict?
Yes, uncertainty about initial conditions can make prediction difficult. Exactly. Determinism describes the rule, not the observer's knowledge or forecasting ability.
What the sources establish
Brownian motion supports statistical predictions rather than exact individual paths.
Sources
Jean Perrin: Nobel Lecture (Nobel Prize Outreach), Brownian motion, Einstein and Smoluchowski, experimental verification