Abstract
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.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Notes
There are, of course, exceptions to this metaphysical bias. For example, Turvey et al. (1981) resist the tendency to delimit intensions to the noetic realm of language and thought and go some way in their attempt to allocate intensions in physical reality. More generally, the extensionalist bias that occupies us here tends to dissolve in a process-based metaphysics. However, these are exceptions and their heterodox character only attests to the grip of extensionalism on mainstream philosophical thought.
By claiming that “on any reasonably naturalistic account of mind and its place in nature” intensional phenomena must, in some sense, be an integral part of nature the intensional phenomena I have in mind are concrete cognitive and linguistic structures. By contrast, abstract entities, for example Fregean thoughts, cannot be considered as partaking in physical reality and, on account of that, ought not to be literally endorsed by naturalists (by contrast, the capacity to construct and to grasp abstractions is, of course, fairly compatible with naturalism).
Doubtless, some readers will be inclined to resist this assertion, arguing that the distinction can be traced further back to medieval philosophy if not to Aristotle himself. While I have no pretensions of being an authority on such matters, I found little evidence to support it. Aristotle’s categories are general types of predication (highest genera, according to some interpretations), and nowhere in the Topics (1987d), or the Categories (1987a), do we find clear evidence that he understood them to be anything like the early-modern notion of intension—the collection of attributes implied by an idea. The medieval notion intentio, rendered as a translation of the terms ma’na and ma’qul which were used in medieval Arabic interpretations of Aristotle, stands, roughly, for a sign in the soul or for whatever it is which stands before the mind in thought (Kneale and Kneale 1962, p. 229; Crane 2000). As such, it can no more be considered a precursor of intension than of intentionality. Perhaps the closest we get to genuine precursors of intension and extension are the notions of significatio and suppositio (respectively) as used in the medieval theory of the properties of terms. Yet, even here the analogy is far from perfect (see Ashworth 2006; Read 2006). Finally, the term intension was, indeed, used during the middle ages but in a different context, namely, in discussions concerning the intension and remission of forms (see Sect. 8).
By ‘propositional structure’ I mean any structure capable of expressing propositional content, whether the structure is cognitive (a representation) or linguistic (a sentence, an utterance). My reason for not using the more familiar term ‘proposition’ is that this term is often associated with Platonic abstract entities, with whose affirmation I would hesitate to align myself.
It is often maintained that C-intensionality is an exclusively linguistic phenomenon, which “has no direct application to any other sort of representational system.” (Dennett 1996, p. 38; see also Crane 2003, p. 34; Zalta 1988, p. 3). However, as Searle observes (1983, p. 25), while C-intensionality is a feature of HOPS, there is no reason to suppose that such HOPS must be linguistic—just as some higher-order sentences and utterances are intensional so do some higher-order intentional states.
One is reminded here of Frege’s celebrated assertion that “[i]n reported speech one talks about the sense, e.g., of another person's remarks.” And that “in this way of speaking words do not have their customary reference but designate what is usually their sense.” (1892, p. 25). However, in contrast with Frege, I would say that it is not senses as such that are being designated in C-intensional contexts but, rather, actual lower-order representations.
As Crane observes (2001, p. 21), not all reports of intentional states are intensional. Some reports do not attempt to capture the subject’s perspective, and, as a result, their truth-value does not depend on the intensions expressed by the intentional states they describe. For example, the sentence “John is thinking of Alaska” does not specify the exact manner under which Alaska is represented in John’s thought; it merely dictates that it is, indeed, Alaska that John is thinking of. Hence, replacing the singular term ‘Alaska’ by a co-extensive expression such as ‘the largest state of the US’ will result in a truth-preserving substitution.
For this reason, it seems to me that Searle is wrong when he insists, with typical verve, that there is no close connection between intensionality-with-an-s and intentionality-with-a-t, and that the only connection between them “is that some sentences about intentionality-with-a-t are intensional-with-an-s”. (Searle 1983, p. 24). Clearly, when it comes to C-intensionality (which seems to be the kind of intensionality he is interested in) Searle’s denial of a close connection to intentionality-with-a-t is untenable as it downplays the fact that the intensionality of attitude reports is a contigent on the intentionality of the reported attitudes.
Thus, even the claim made in Sect. 2.2 to the effect that C-intensionality follows from the intensional character of (the having of intensions by) intentional states is rarely represented in the relevant literature.
To be sure, noetic entities refer to many things beside properties (objects, situations, events, etc.); nevertheless, as I argue below, the intensional aspect of semantic valuation lies in predication, and the latter consists in property ascription.
A complete argument in favor of the claim that properties are the quintessential intensional phenomena requires, in addition to the account provided below, a demonstration that the intensionality of modal-terms contexts can also be traced to the nature of properties. I believe that such an account can be given for causal modal statements, where the modal force of such statements is analyzed in terms of the dispositional potency of the properties that sustain the truth makers of such statements (along the lines suggested by Martin and Heil 1999). However, in accordance with my decision not to discuss M-intensionality in any detail here (see Sect. 2.2), I shall not elaborate on this topic any further.
As the terms ‘coarse-grained’ and ‘fine-grained’ suggest, the distinction is often taken to imply that two fine-grained intensions, say two logically equivalent concepts, may be distinct despite corresponding to, or expressing, identical properties (Bealer 2000). While this is a controversial point, I shall not pursue the issue any further. By helping myself into this familiar terminology I assume neither more, nor less, than the fact that it corresponds to the distinction between noetic and non-noetic intensional entities.
An alternative way to make the point is this. Intentional states represent their intentional objects under definite aspects and their aspectual character is definitive of their identity qua content bearing intentional states (cf. Searle 1992, p. 155). A mental state S whose content can be expressed by the proposition “all pelicans are feathered” represents pelicans as feathered. Representing under this aspect is constitutive of S’s semantic identity. A co-extensive mental state S′, representing pelicans as possessors of intertarsal joints, shares with S the same intentional objects but its content is nevertheless different due to the fact that it represents those objects under a different aspect.
From now on I shall use properties in a wide sense, which includes also many-place relations. The claim advanced in this section, then, is that the intensional character of noetic intensional entities depends on the intensional character of the properties and relations they express.
As Cornman notes, this is one way to state the thesis of the unity of science. The demand that all predicates employed by science will be couched in an extensionalist physical language was meant to undermine the dichotomy between the physical sciences and the sciences of the spirit (the Geisteswissenschaften), presumably the natural abode of intensional entities.
Lest the reader gets confused with the switch between ‘intentional’ and ‘intensional,’ it may be pointed out that at least some of Chisholm’s ‘criteria of intentionality’ are unmistakably criteria of intensionality, i.e., criteria that demonstrate the irreducible intensionality of intentional idioms. In contrasting intentional vocabulary with extensional vocabulary, then, Quine is tacitly presupposing the irreducible intensionality of the former. Unfortunately, Chisholm himself is not explicit about the fact that his discussion of intentionality is, to a large degree, a discussion of intensionality, a confusion replicated by other authors as well (e.g., Fodor and Pylyshyn 1981, p. 188ff).
As explained in Sect. 6, my claim regarding the categorical differences between objects and properties pertains to the futility of all attempts to reduce properties to a strictly extensionalist ontology. However, it need not suggest the absurd idea that properties and objects have nothing to do with each other. In other words, we can still speak meaningfully of objects ‘exemplifying properties’ and of properties as being, in some sense, ‘constitutive’ of objects.
Thus, modulo the admission of sets (whose admission is grounded in their theoretical expediency), both David Lewis’s and Quine’s ontologies are exemplars of nominalism (although, unlike Lewis, Quine believes that the admission of sets disqualify his ontology from being one). A still more austere nominalism is defended by Sellars (1967).
Another important contemporary alternative to either Platonism or nominalism is Armstrong’s (e.g., Armstrong, 1978, 1989) Aristotelian conception of properties as in rebus universals, i.e., as denizens of spatiotemporal reality, wholly present in each of their numerically distinct instances. As my sympathies lie elsewhere, I shall not discuss Armstrong’s conception of properties as immanent universals any further.
Giving up the idea that identical properties might be shared is a potential source of concern insofar as it presupposes a primitive notion of similarity and deprives us of the ability to explain similarity in terms of the sharing of universals (I am indebted to Ariel Meirav for turning my attention to this problem.). See Heil (2003, chap. 14), however, for an argument that no high stakes are involved in the adoption of a primitive notion of perfect similarity. Be that as it may, I shall not dwell on the issue any further since my intention is not to provide a systematic argument in favor of trope theory but merely to indicate that there exists a coherent and, in many respects, attractive alternative to the identification of properties with universals.
Notably, Leibniz’s philosophical system offers a rare example of an early alternative to extensionalism.
Both Arnauld and Leibniz, who used ‘extension’ to refer to a semantic category, were thoroughly familiar with Descartes’ notion of matter as res extensa.
Physical objects are identical when co-extensive (physical sense), and abstract objects, such as sets, are identical when the objects over which they extend (semantic sense) are co-extensive (in either the physical, or the semantic sense).
Of course, properties such as solidity and impenetrability may come in degrees, hence be measurable, insofar as complex bodies (bodies, say, that are made as configurations of atoms) may be more or less solid, or impenetrable. But the point is that the ultimate constituents of nature (e.g., the atoms of Newton, or the corpuscles of Boyle) were taken to be solid and impenetrable in an absolute and unvaried sense.
Carnap himself is sympathetic to the view that not all extensive magnitudes are additive. For example, relativistic velocity (in contradistinction with Newtonian velocity) is, on his account, a non-additive extensive magnitude. However, Carnap also accentuates that (a) the question whether non-additive extensive magnitudes are, indeed, extensive is, to a large extent, a matter of convention; (b) that many authors identify extensive magnitudes with additive magnitudes, and that “[t]here is no need to criticize such usage” (1966, p. 76); and (c) that, in any case, even on his more liberal approach the vast majority of extensive magnitudes are additive.
The point is made by Russell in his discussion of extensive quantities and intensive quantities in On The Relations of Number and Quantity (1897, pp. 331–332). Russell himself attributes this observation to Hegel.
The essence of this insight was, I believe, captured by Leibniz in asserting that extension expresses nothing but a “simultaneous diffusion or repetition of some particular nature, or what amounts to the same thing, a multitude of things of this same nature which exist together with some order between them” (GP II 269/L536, quoted in Rutherford 1998, p. 248).
In medieval times the term ‘mode’ had a variety of different senses none of which corresponded exactly to the notion of accident.
This assertion is, I think, true regardless of the fact that Aristotle’s conception of substantive forms underwent some important modifications during the Middle-ages (see, e.g., Pasnau 2004).
Of course, even if objects and properties are mutually irreducible it may well be that both are reducible to some third category. Indeed, this seems to be the credo of process philosophies (e.g., Bickhard 2000; Whitehead 1929/1969). Attractive as this possibility may be, exploring it is beyond the scope of this paper.
By ‘atomism’ I have in mind the view that, in its most fundamental level of existence, physical reality consists of a basic set of mutually separated, or separable, chunks of matter. Thus, I am concerned with the conceptual thread that connects the atomism of Leucippus and Democritus to the corpuscularianism of 17th century dynamics, to more recent articulations of a mechanistic physical framework. This being so, the critique of atomism implicated in the discussion that follows is not directed against the process atomism (i.e., the atomism of acts of becoming) suggested in the works of Whitehead and his followers (see, e.g., Whitehead 1929/1969, p. 41; Leclerc 1958, pp. 71–74).
This last observation converges, I believe, with Martin and Heil’s (1999) view that every property is at once dispositional and qualitative, from which it follows that the possession of a quality is always dispositionally operative.
The introduction of fields as pivotal entities in the electromagnetic theories of Faraday and Maxwell can be seen as an even earlier “crack” in the atomistic worldview, but it wasn’t until Einstein’s relativity theory that fields were recognized as independent entities, irreducible to any underlying mechanical medium.
According to quantum field theory even the vacuum is the locus of vibrating energy levels, pulsating in endless rhythms of creation and destruction of virtual particles (see, e.g., Saunders and Brown 1991). Hence not only are the atoms of classical atomism an outdated notion but so is its notion of the void.
This seems to be the sense poetically employed by Milton: “Let not my words offend thee, Heavenly Power/ My maker, be propitious while I speak/ Hast thou not made me here thy substitute/ And these inferior far beneath me set?/ Among unequals what society/ Can sort, what harmony or true delight?/ Which must be mutual, in proportion due/ Given and received, but, in disparity/ The one intense, the other still remiss” (Paradise Lost, 1981, XIII, pp. 380–385).
In the beginning of “Two dogmas of Empiricism” meanings are portrayed as the ghostly remnants of the Aristotelian notion of essence (see footnote 26). It is then suggested that, once separated from the theory of reference, the theory of meaning boils down to “the synonymy of linguistic forms and the analyticity of statements,” while “meaning themselves, as obscure intermediary entities, may well be abandoned” (p. 242). Immediately after, Quine proceeds to argue that there is no informative account of synonymy or of analyticity, an argument whose conclusion is, in effect, that there are no meanings, and that semantics must be wholly extensional.
Observe, in particular, that the medieval notion ‘intentio,’ a precursor of our modern notion of intentional content, stood for a concept, or sign in the soul, representing the form of external things and was, in turn, an elaboration of Aristotle’s contention that the soul becomes aware of things by receiving their forms without receiving their matter (On The Soul, III, 2 425 b25).
Reference
Aristotle (1987a) Categories. Selections in Ackrill JL (ed) A new Aristotle reader. Oxford University Press, Oxford
Aristotle (1987b) On the soul. Selections in Ackrill JL (ed) A new Aristotle reader. Oxford University Press, Oxford
Aristotle (1987c) Metaphysics. Selections in Ackrill JL (ed) A new Aristotle reader. Oxford University Press, Oxford
Aristotle (1987d) Topics. Selections in Ackrill JL (ed) A new Aristotle reader. Oxford University Press, Oxford
Armstrong DM (1978) A theory of universals. Cambridge University Press, Cambridge
Armstrong DM (1989) Universals: an opinionated introduction. Westview Press, Boulder, CO
Arnauldt A (1662/1850) Logic, or the art of thinking: The Port-Royal logic (trans. Baynes TS). Sutherland & Knox, Edingburgh
Ashworth JE (2006). Medieval theories of singular terms. Stanford Encyclopedia of Philosophy (online)
Bealer G (2000) Intensional entities. Routledge Encyclopedia of Philosophy, pp 803–806
Bickhard MH (2000) Emergence. In: Andersen PB, Emmeche C, Finnemann NO, Christiansen PV (eds) Downward causation. University of Aarhus Press, Aarhus, Denmark, pp 322–348
Bohm D (1980) Wholeness and the implicate order. Routledge and Kegan Paul, London
Born M (1962) Einstein’s theory of relativity. Dover Publications, NY
Carnap R (1937) The logical syntax of language. Routledge and Kegan Paul, London
Carnap R (1966) Philosophical foundations of physics: an introduction to the philosophy of science. Basic Books, NY
Chisholm R (1957) Perceiving: a philosophical study. Cornell University Press, Ithaca
Claget M (1950) Richard Swineshead and Late Medieval physics: I. The intension and remission of qualities. Osiris 9:131–161
Cornman JW (1962) Intentionality and intensionality. Philos Quart 12:44–52
Crane T (2000) Intentionality. Routledge Encyclopedia of Philosophy
Crane T (2001) Elements of mind: an introduction to the philosophy of mind. Oxford University Press, London
Crane T (2003) The mechanical mind: a philosophical introduction to minds, machines and mental representation. Routledge, NY
Davis PCW (1979) The forces of nature. Cambridge University Press, NY
Davis PCW (1984) Particles do not exist. In: Christensen SM (ed) Quantum theory of gravity. Adam Hilger, pp 66–77
Dennett DC (1996) Kinds of minds. Basic Books, NY
Fodor JA (1974) Special sciences: the disunity of science as a working hypothesis. In: Block N (ed) 1980, Readings in philosophy of psychology, vol 1. Harvard University Press, Cambridge, MA, pp 120–133
Fodor JA, Pylyshyn ZW (1981) How direct is visual perception?: some reflections on Gibson’s “ecological approach”. Cognition 9:139–196
Follesdal D (1969) Husserl’s notion of noema. J Philos 66:680–687
Follesdal D (1974). Meaning and experience. In: Guttenplan S (ed) Mind and language: Wolfson College Lectures 1974. Oxford University Press, Oxford
Follesdal D (1990) Noema and meaning in Husserl. Philos Phenomenol Res 50(Suppl):263–271
Frege G (1892/1997) On Sinn and Bedeutung. Reprinted in Beany M (ed) The Frege reader. Blackwell, Malden, MA
Frege G (1893/1964) The basic laws of arithmetic. Translated by M. Furth. University of California Press, Berkeley
Grant E (1977) Physical science in the Middle Ages. Cambridge University Press, West Hanover, MA
Greene B (1999) The elegant universe: superstrings, hidden dimensions, and the quest for ultimate theory. W.W. Norton, NY
Hay WH (1952) Nicolaus Cusanus: the structure of his philosophy. Philos Rev 61(1):14–25
Heil J (2003) From an ontological point of view. Oxford University Press, Oxford
Hiley BJ (1991) Vacuum or holomovement. In: Saunders S, Brown HR (eds) The philosophy of vacuum. Clarendon Press, Oxford, pp 217–250
Kim J (1993) Supervenience and mind. Cambridge University Press, Cambridge
Kim J (1998) Mind in a physical world: an essay on the mind-body problem and mental causation. Bradford/MIT, Cambridge, MA
Kneale WC, Kneale M (1962) The development of logic. Clarendon Press, Oxford
Koyr’e A (1968) Newtonian studies. University of Chicago Press, Chicago
Küppers BO (1992) Understanding complexity. In: Beckermann A, Flohr H, Kim J (eds) Emergence or reduction? Essays on the prospects of non-reductive physicalism. Walter and Gruyter, Berlin, pp 241–256
Leclerc H (1958) Whitehead’s metaphysics. George Allen and Unwin, London
Leibniz GW (1677) Letter to Arnold Eckhard. Reprinted in Leibniz GW (1969) Philosophical papers and letters (translated and edited by L.E. Loemker). Reidel, Dordrecht
Leibniz GW (1690/2000) New essays on human understanding. Cambridge University Press, Cambridge
Lewis D (1983) Philosophical papers, vol I. Oxford University Press, NY
Lewis D (1986) On the plurality of worlds. Blackwell, Oxford
Mahoney EP (1987) Lovejoy and the hierarchy of being. J Hist Ideas 48(2):211–230
Martin CB (1980) Substance substantiated. Aust J Philos 58:3–10
Martin CB (1996) Properties and dispositions. In: Crane T (ed) Dispositions: a debate. Routledge, London, pp 71–87
Martin CB, Heil J (1999) The ontological turn. Midwest Stud Philos XXIII:34–60
Milton J (1981) Paradise lost. Mentor, NY
Neurath A (1931/1983) Protocol Satze. Erkenntnis. Reprinted in Cohen RS, Neurath M (eds) Philosophical papers 1913–1946. Reidel, Dordrecht
Pasnau R (2004) Form, substance, and mechanism. Philos Rev 113:31–88
Quine WVO (1953) Two dogmas of empiricism. In: Quine WVO (ed) From a logical point of view. Harvard University Press, Cambridge, MA
Quine WVO (1960) Word and object. John Wiley & Sons, and MIT Press, Cambridge, MA
Read S (2006) Medieval theories: properties of terms. Stanford Encyclopedia of Philosophy (online)
Russell B (1897) On the relations of number and quantity. Mind 6(23):326–341
Rutherford D (1998) Leibniz and the rational order of nature. Cambridge University Press, NY
Saunders S, Brown HR (1991) The philosophy of vacuum. Clarendon Press, Oxford
Searle JR (1983) Intentionality: an essay in the philosophy of mind. Cambridge University Press, Cambridge
Searle JR (1992) The rediscovery of the mind. MIT/Bradford, Cambridge, MA
Sellars W (1967) Abstract entities. In Philosophical perspectives. Charles C. Thomas, Springfield, IL
Shapiro H (1959) Walter Burley and the intension and remission of forms. Speculum 34(3):413–427
Sherry DF (1998) The ecology and neurobiology of spatial memory. In: Dukas R (ed) Cognitive ecology: the evolutionary ecology of information processing, and decision making. University of Chicago Press, Chicago
Spencer M (1971) Why the “S” in “Intension”? Mind 80(317):114–115
Swoyer C (2000) Properties. Stanford Encyclopedia of Philosophy (online)
Turvey MT, Shaw RE, Reed ES, Mace WM (1981) Ecological laws of perceiving and acting: In reply to Fodor and Pylyshyn (1981). Cognition 9:237–304
Weinberg S (1977) The search for unity, notes for a history of quantum field theory. Daedalus 106(4):17–35
Whitehead AN (1929/1969) Process and reality. Free Press, NY
Whitehead AN, Russell BAW (1910–1913, 2nd edn., 1925–1927). Principia mathematica, vol. 1. Cambridge University Press, Cambridge
Williams DC (1953) On the elements of being: I. Rev Metaphys 7(1):3–18
Wilson NL (1955) Space, time, and individuals. J Philos 52(22):589–598
Zalta EN (1988) Intensional logic and the metaphysics of intentionality. MIT Press, Cambridge, MA
Acknowledgements
Thanks are due to Mark Bickhard, Marcelo Dascal, David Martens, Scott Stapleford, and an anonymous referee of this journal.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Shani, I. The Myth of Reductive Extensionalism. Axiomathes 17, 155–183 (2007). https://doi.org/10.1007/s10516-007-9016-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10516-007-9016-x