, Volume 17, Issue 2, pp 155–183 | Cite as

The Myth of Reductive Extensionalism

  • Itay ShaniEmail author
Original Paper


Extensionalism, as I understand it here, is the view that physical reality consists exclusively of extensional entities. On this view, intensional entitities must either be eliminated in favor of an ontology of extensional entities, or be reduced to such an ontology, or otherwise be admitted as non-physical. In this paper I argue that extensionalism is a misguided philosophical doctrine. First, I argue that intensional phenomena are not confined to the realm of language and thought. Rather, the ontology of such phenomena is intimately entwined with the ontology of properties. After providing some evidence to the popularity of extensionalism in contemporary analytic philosophy, I investigate the motivating reasons behind it. Considering several explanations, I argue that the main motivating reason is rooted in the identification of matter with extension, an identification which is one of the hallmarks of the mechanistic conception of nature inherited from the founding fathers of our modern scientific outlook. I then argue that such a conception is not only at odds with a robust ontology of properties but is also at odds with our best contemporary physics. Rather than vindicating extensionalism contemporary science undermines the position, and the lesson to be drawn from this surprising fact is that extensionalism needs no longer be espoused as a regulative ideal of naturalistic philosophy. I conclude by showing that the ontological approach to intensional phenomena advocated throughout the paper also gains support from an examination of the historical context within which ‘intension’ was first introduced as a semantic notion.


Extensional entities Extensionalism Intensional entities Mechanistic philosophy Modes Naturalism Properties 



Thanks are due to Mark Bickhard, Marcelo Dascal, David Martens, Scott Stapleford, and an anonymous referee of this journal.


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© Springer Science + Business Media B.V. 2007

Authors and Affiliations

  1. 1.Department of Philosophy, School of Social SciencesUniversity of the WitwatersrandWits, JohannesburgSouth Africa

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