1. The problem statement, all variables and given/known data I keep seeing this crop up throughout my QM course but i still don't understand what a "good" set of commuting observables would be. . Surely any set of observables that commute have to be a good set? I may just be stating the obvious but the way its phrased it makes me feel as though some observables that commute may be 'better' for some reason than another set that also commute but I don't understand why thats the case. Like if you have a couple of operators such that [a, b] = 0 and [a, c] = 0 are they both as good as each other for describing a quantum system or what? To me this says that observables for both a and b, or a and c can be found simultaneously so neither is a better set? 2. Relevant equations N/a 3. The attempt at a solution Pretty much explained my thoughts on the matter above, its not so much a homework question as it is just clarification.