A remark on Field's evaluative notion of Apriority
There are many ways to update a belief system. For example, 1) believe every proposition that comes to your mind; 2) believe everything that makes you feel good; 3) believe everything Reverend Moon says. In "A Priority as an Evaluative Notion", Hartry Field argues that there is no fact of the matter as to which way is best.
In one sense, this is trivial. Of course the normative question which way you should choose does not have a purely factual answer. Which way you should choose depends on what you want from your belief system.
In another sense, Field's claim is obviously false. Given that you want your belief system to be true, some ways are objectively better than others, namely those that more reliably yield truths. (We don't merely want our belief system to be true. Among other things, we also want it to tell us something about matters we're interested in. Like truth, these further aims constrain acceptable methodologies.)
Of course, showing that some methodology is better than another always presupposes a methodology. This is because 'showing' means 'supporting the belief', and you can't support a belief without using a belief-supporting method.
Now what does all this have to do with Apriority?