# Bayesian Confirmation Theory: Inductive Logic or Mere Inductive Framework?

Published: *Synthese*, 141:365–379. 2004.

Abstract:
To what extent is Bayesianism a positive confirmation theory, delivering particular judgements as to how evidence bears on scientific theories, and to what extent is it, as Colin Howson (*Hume's Problems*) has recently claimed, more like a framework for confirmation theory capable of accommodating any kind of substantive inductive assumption about the proper relation between evidence and theory? I ask these questions of what is perhaps the most popular version of Bayesian confirmation theory, that presented recently in Howson and Urbach's *Scientific Reasoning* and Earman's *Bayes or Bust?*, which I call, after Earman, *modern Bayesianism*. I conclude that

- Modern Bayesianism is more of a positive confirmation theory than Howson suggests, but that
- The principal source of modern Bayesianism's positive judgments of inductive relevance is not the Bayesian machinery itself, but rather what David Lewis calls the
Principal Principle

.

I then explain why the Principal Principle has, incorrectly, not traditionally been regarded as an inductive assumption.

See a PDF version of the paper.