Revising a system of beliefs › Revision without permission to believe anything

Section 6 describes differences between relatively peripheral claims and central commitments, including logic and mathematics. Peripheral claims have more direct connections with particular experiences. Revising central commitments can require much wider changes. Quine denies an absolute immunity from revision while retaining these differences in role and cost.

His claim that a statement can be retained through adjustments elsewhere should therefore be read with the costs in view. Preserving a claim may require rejecting an observation report or changing other commitments substantially. The availability of such a manoeuvre does not establish its wisdom. Rational assessment still concerns how well the resulting system accommodates experience and how disruptive the repair is.

Consider an invented device manufacturer that blames every failed test on interference. One interference explanation may be independently supported. A series of unsupported explanations introduced solely to protect the device adds assumptions without explaining why the failures occur where they do. Holism makes it necessary to assess the wider package; it does not confer credibility on every package that can be described.

Quine emphasizes considerations such as simplicity and conservatism in revising theory. These guide choices within inquiry. They are not a recipe that guarantees a unique repair for every surprise, and conservatism alone would not establish that an entrenched belief is true. Quine, §6.

Pragmatic criteria for choosing theories answer a different question from a definition of truth. The discussion of conservatism and simplicity does not by itself establish that truth is whatever inquiry eventually converges upon. "Two Dogmas" argues about meaning, empirical significance, and theory revision. Practical convenience alone does not guarantee that a proposition is true; we still need to assess how the theory accommodates experience.