This paper defines and analyses the concept of a 'ranking problem'. In a ranking problem, a set of objects, each of which possesses some common property P to some degree, are ranked by P-ness. I argue that every eligible answer to a ranking problem can be expressed as a complete and transitive 'is at least as P as' relation. Vagueness is expressed as a multiplicity of eligible rankings. Incommensurability, properly understood, is the absence of a common property P. Trying to analyse incommensurability in the same framework as ranking problems causes unnecessary confusion.