  It is now a familiar claim in general philosophy that, in the case of certain objects and phenomena, an account of their nature is not built into the understanding that is sufficient for competent use of the words that refer to them (or into the understanding of the relevant concepts that is sufficient for competent thinking). Such understanding, captured in criteria of application and truths shared among competent users, does not provide sufficient metaphysical guidance. In many cases, such understanding includes an open-ended clause that allows for the existence of a certain kind of explanation of the nature of the objects, or, at least, that understanding does not rule out some such explanation, yet certainly falls short of picking out any particular explanation from among the eligible ones. In such cases, substantive investigation is indispensable to a complete explanation of the nature of the relevant object, and often must come first, before we realize that it is indeed germane to the nature of the object (Kripke 1980; Burge 1986; Rey 1998; Williamson 2007; Stavropoulos 1996, 2012). 