The Frege-Geach problem and Blackburn's expressivism

(2020), Philosophia, 48(5): 2021-2031 (co-author with Plato C.Y. Tse)

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Blackburn has outlined a formal account for moral expressivism, and we argued that the moral Frege-Geach problem can be solved formally by appending two rules for the boo-operator which are missing from his account. We then extended Blackburn’s formal account to generate a similar solution to the problem in modal context and showed that the validity of the modal argument can be preserved too in modal expressivism. However, the higher-order element endorsed by Blackburn does not seem necessary for solving the Frege-Geach problem. Nor is his extension from moral expressivism to modal expressivism tenable, since the latter violates its own ontological constraint. A general moral is drawn on the basis on three observations made in evaluating Blackburn’s expressivism.

Trespassers and existential import

(2019), Thought, 8(1): 57-62 (co-author with Kai-yee Wong)

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It is a received view of the post-Fregean predicate logic that a universal statement has no existential import and thus does not entail its particular (existential) counterpart. This paper takes issue with the view by discussing the trespasser case, which has widely been employed for supporting the view. The trespasser case in fact involves a shift of context. Properly understood, the case provides no support for the received view but rather suggests that we rethink the ‘quantity view’ of the existential import of quantifiers.

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Alik Pelman (2014) proposes a sceptical challenge to the widely accepted thesis that theoretical identities are necessary. His argument relies on the possibility of the manifest criterion of identity. In this article, we argue that given the necessity of the obtaining of the identity criterion, Pelman’s sceptical argument against the necessity of theoretical identities cannot be effective. By comparing Pelman’s sceptical argument with classical sceptical arguments, it is demonstrated that there is a sense in which classical arguments are effective but not Pelman’s.