The starting step of inquiry

To define a thing is to select among the whole of its properties those which should be understood to be designated and declared by its name; the properties must be very well known to us before we can be competent to determine which of them are fittest to be chosen for this purpose.

Every proposition consists of two names [concepts]: and every proposition affirms or denies one of these names of the other . . . Here therefore we find a new reason why the signification of names, and the relation generally between names and the things signified by them must occupy the preliminary stage of inquiry we are engage in.

J.S. Mill. (From Goertz "Social science concepts: A user's guide" (2006).