Reducing reductionism: on a putative proof for Extreme Haecceitism Troy Thomas Catterson Published online: 14 July 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Nathan Salmon, in his paper Trans-World Identification and Stipulation (1996) purports to give a proof for the claim that facts concerning trans-world identity cannot be conceptually reduced to general facts. He calls this claim ‘Ex- treme Haecceitism.’ I argue that his proof is fallacious. However, I also contend that the analysis and ultimate rejection of his proof clarifies the fundamental issues that are at stake in the debate between the reductionist and haecceitist solutions to the problem of trans-world identity. These issues hinge on the ability of modal logic and possible worlds semantics to draw a hard and fast distinction between the logic and the metaphysics of modal logic. I shall claim that the considerations in this paper call into question the viability of such a distinction. Keywords Transworld identity Á Haecceitism Á Essentialism Á Modal metaphysics Á Reductionism 1 The problem of Trans-world Identity, the question as to how cross-world identities are grounded in the possible worlds account of modality de re, boils down to one crucial assumption. This is the assumption that cross-world identities need to be grounded at all, that in order for statements of trans-world identity to make sense, there must be a set of sufficient or necessary conditions met by the individuals in the worlds in question that do not involve irreducible reference to these very individuals. T. T. Catterson (&) Philosophy, North Georgia College and State University, Dunlap Hall, College Circle, Dahlonega, GA 30533, USA e-mail: ttcatterson@ngcsu.edu 123 Philos Stud (2008) 140:149–159 DOI 10.1007/s11098-007-9134-8