[SydPhil] UNSW Philosophy Event Invitation: Leibniz’s Law, Multisets, and the Puzzle of Abstract Duplicates - 5 Aug

Tue Jul 29 16:05:34 AEST 2025

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From: Humanities & Languages School Office <hal at unsw.edu.au>
Sent: Monday, 28 July 2025 4:08 PM
Subject: HAL Event Invitation: Leibniz’s Law, Multisets, and the Puzzle of Abstract Duplicates - 5 Aug

[UNSW]

Leibniz’s Law, Multisets, and the Puzzle of Abstract Duplicates

Leibniz’s Principle of the Identity of Indiscernibles (PII) maintains that no two distinct entities share all properties. Multisets, however, appear to refute this principle: the multiset [2,2] apparently contains two numerically distinct yet qualitatively identical occurrences of the number 2. After clarifying the formal theory of multisets, this paper evaluates and rejects three standard responses: (1) re‑classifying duplicates as concrete tokens, (2) invoking primitive haecceities, and (3) reducing multiplicity to mere syntactic coding. Each approach either distorts mathematical practice or trivializes PII. An alternative, idealist‑structural account is proposed: multiplicity arises from the external act of counting, so duplicate entries differ only in their relational positions while the counted object remains intrinsically identical. By relocating plurality in acts of enumeration rather than in the enumerated items, the proposal preserves PII without resorting to ad hoc metaphysics and clarifies the conceptual foundations of abstract duplication.

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Plato Tse
Plato Tse is Associate Professor in Philosophy at National Chengchi University, Taipei. He received his Dr. phil. from Ludwig‑Maximilians‑Universität München (2018), following an MPhil at The Chinese University of Hong Kong and a double‑major BA in Philosophy and German at the University of Hong Kong. His work spans classical German philosophy—especially Fichte, Kant, and their Leibnizian heritage—and contemporary metaphysics of modality and abstract objects. Funded by Taiwan’s National Science and Technology Council, his recent projects address (i) Leibniz’s Law and the ontology of abstract duplicates (2024–26), (ii) Fichte’s transcendental philosophy (2023–24), and (iii) the constitutive role of mind in idealism (2021–24). His articles have appeared in Epoché, Philosophy Compass, the Journal of Transcendental Philosophy, Philosophia, and Inquiry.

A light lunch will be provided.

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5 August 2025

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12:30pm—2:00pm

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UNSW Kensington

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Morven Brown (C20) L2 238

For more information

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j.phillips at unsw.edu.au<mailto:j.phillips at unsw.edu.au>

School of Humanities & Languages
Faculty of Arts, Design and Architecture

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