Credence
Credence is your degree of belief in a proposition, typically modelled as a number in .
- 0 = certain it’s false
- 1 = certain it’s true
- 0.5 = perfectly undecided
Why grade belief instead of yes/no?
Unlike binary belief (believe / don’t believe), credence captures graded confidence: the natural currency of ampliative reasoning.
How evidence updates credence
Good evidence raises credence in a hypothesis; disconfirming evidence lowers it. The Bayesian formalization is conditional probability, but the informal idea is enough: an observation that the hypothesis predicts (and that competitors don’t) is strong evidence.
Why credence, not certainty
Insisting on certainty before believing anything leads to paralyzing skepticism. Insisting on no evidence at all leads to credulity. Credence sits between: believe in proportion to the evidence.
Affirming the Consequent is deductively invalid, but reading it as a credence update rescues it as legitimate ampliative reasoning. Observing what a hypothesis predicts doesn’t prove the hypothesis; it raises your credence in it.