ABSTRACT
The most obvious answer to the question of what justifies our prior credences is that they are justified by our perceptions. Thus in the cointossing case of chapter 7.VII, seeing that a coin is double-headed can both cause and justify a full belief — a credence at or very close to 1 — in the proposition A2 that it is double-headed. However, to make this answer as useful as it is obvious, we must first remove an ambiguity in ‘I see that A’, ‘I hear that A’ etc., statements which may or may not be taken to entail that I fully believe the proposition A, and also that A is true. I shall take them to entail neither. That is, I shall assume that, when for example we see a conjuror pull a rabbit out of an empty hat, we need not believe what we see, and it need not be true.
