Posteriors

The Result of Updating

A posterior is the confidence one should hold after considering new evidence. It is not merely the prior, and it is not merely the new evidence. It is the result of their interaction.

In informal reasoning, a posterior is the answer to: after seeing this, where should my confidence now land?

Why Posteriors Matter

Posteriors matter because inquiry is sequential. Today posterior becomes tomorrow prior. If updates are too dramatic, belief becomes unstable. If updates are too small, belief becomes stubborn. Good credencing seeks responsiveness without volatility.

Posterior vs Assigned Credence

The posterior is the credence warranted by the update. Assigned Credence (CA) is what the agent actually adopts. In an ideal case, they match. When they diverge, the model asks whether some core-rational force is overriding the update.

Adjacent References

These are starting points rather than exhaustive citations. They connect this page to nearby work in probability, calibration, cognitive bias, and social epistemology.

• |Thomas Bayes, "An Essay towards solving a Problem in the Doctrine of Chances" (1763).
• |E. T. Jaynes, Probability Theory: The Logic of Science (2003).