  As an account of the distinctive generality of logic, then, permutation invariance has much to recommend it. It is philosophically well-motivated and mathematically precise, it yields results that accord with common practice, and it gives determinate rulings about some borderline cases (for example, set-theoretic membership). Best of all, it offers hope for a sharp and principled demarcation of logic that avoids cloudy epistemic and semantic terms like “about”, “analytic”, and “a  priori”.[14]