PHI403 Lecture 15 — Credence: Probability from Uncertainty

The first of three lectures on probability in causal reasoning. The key distinction:

Ontological probability (chance) — there are probabilistic causes in the world; drunk driving genuinely raises the probability of an accident.
Epistemological probability (credence) — causes are absolute (yes or no), but our knowledge is limited; probability is a degree of belief.

For a causal determinist, once the initial conditions are fixed (coin tossed, Big Bang happened), the outcome is determined — Laplace's demon would know it. All probability talk is then credence.

Chaos theory complicates the picture: the world is deterministic, but outcomes are unpredictable in principle because the system is hypersensitive to initial conditions no finite specification can fix (weather forecasting).

Bayesian reasoning operates in the credence register: priors get updated by evidence; the maximum degree of belief is 1. The lecture closes with three reflective questions: can a hypothesis be held so strongly that no counter-evidence would lower one's credence? Can it be held so weakly that no evidence would raise it? Does prior confidence affect what counts as relevant evidence?

Connections

Back-link: sources/2023-anjum-rocca-phi403-causation-in-science. Concepts: concepts/probabilistic-causation · concepts/aleatoric-vs-epistemic-uncertainty · concepts/causation.