   Saul Kripke (1972) noticed an important difference between the behavior of a proper name and the behavior of a coreferential definite description expressing a contingent or non-essential property of its referent, in modal contexts. Consider two sentences (9) and (10), each containing some modal operator like ‘might’ (that expresses a possibility) and such that the former contains a proper name while the latter contains a coreferential definite description: