The identity of indiscernibles is false. Robert Adams and others have argued that if the identity of indiscernibles is false, then primitive thisness must be admitted as a fundamental feature of the world (i.e. haecceitism is true). Moreover, it has been suggested that if haecceitism is true, then essentialism is false - that accounting for individuation by means of haecceities precludes a thing's having essential qualitative properties. I will argue that this suggestion is misguided. In so doing, I will be defending what Adams has labeled 'moderate haecceitism'.After working through some preliminary issues, I will attempt (in section I) to motivate haecceitism. I will begin by reviewing Adams' arguments against the doctrine of the identity of indiscernibles. Next, I will examine altemative accounts of individuation which concede the falsity of that doctrine. I will reject these accounts and conclude that primitive thisness has an essential role to play in any satisfying account of individuation. In section II , I will surface the alleged tension between haecceitism and essentialism. In section III , I will suggest that Adams' moderate haecceitism avoids the tension surfaced in section II. Finally, in section IV, I will raise a difficulty for Adams' view and suggest a different understanding of the nature of haecceities. I will argue that the alleged tension between haecceitism and essentialism rests on a conflation of the metaphysical problem of individuation either with the epistemological problem which goes by the same name or with problems involving the unity of a thing. I will conclude with a few brief comments about the significance of moderate haecceitism for modal epistemology.

Analytic Philosophy