Essentialism: Metaphysical or Psychological? Moti Mizrahi Philosophy Department St. John's University 8000 Utopia Parkway Queens, NY 11439 USA Email: motimizra@gmail.com Abstract: In this paper, I argue that Psychological Essentialism (PE), the view that essences are a heuristic or mental shortcut, is a better explanation for modal intuitions than Metaphysical Essentialism (ME), the view that objects have essences, or more precisely, that (at least some) objects have (at least some) essential properties. If this is correct, then the mere fact that we have modal intuitions is not a strong reason to believe that objects have essential properties. Keywords: essence; essential properties; heuristic; inference to the best explanation; metaphysical essentialism; modal intuition; psychological essentialism 2 1. Introduction Metaphysical Essentialism (ME) "is the doctrine that (at least some) objects have (at least some) essential properties" (Robertson 2008). More precisely (Paul 2004: 170): an object O has property P essentially when O must have P in order to be the object that it is. If O has P essentially, then, necessarily, in any world in which O exists, O must have P. (See also Mackie 2006: 1.) ME, then, is "a theory of the objective, context-independent de re nature of objects" (Paul 2004: 170). But why think that objects have an "objective, context-independent de re nature"? In this paper, I am not concerned with how to characterize the distinction between essential properties and accidental properties (see, e.g., Gorman 2005). Rather, I am concerned with whether or not there are strong reasons to believe that objects even have "objective, context-independent de re natures." In other words, why think that objects have essences? 1 I discuss empirical evidence that suggests that, for all we know, we project essences onto objects in much the same way that, according to Hume, we project necessary connexion onto events. In other words, in this paper, I seek to do to the notion of essence what Hume did to the notion of necessary connexion. In An Enquiry Concerning Human Understanding (7.28), Hume (1975: 75) argues as follows: 1 As Robertson (2008) writes, "Accounts of the first sort [i.e., those that suggest that claims of origin essentialism are grounded in a "branching conception of possible worlds"] (offered by J. L. Mackie (1974) and P. Mackie (2006)) have aimed not so much to argue for origin essentialism as to explain why we find such claims attractive" (emphasis added). For example, see Brogaard and Salerno (2007). 3 It appears, then, that this idea of a necessary connexion among events arises from a number of similar instances which occur of the constant conjunction of these events; nor can that idea ever be suggested by any one of these instances, surveyed in all possible lights and positions. But there is nothing in a number of instances, different from every single instance, which is supposed to be exactly similar; except only, that after a repetition of similar instances, the mind is carried by habit, upon the appearance of one event, to expect its usual attendant, and to believe that it will exist. This connexion, therefore, which we feel in the mind, this customary transition of the imagination from one object to its usual attendant, is the sentiment or impression, from which we form the idea of power or necessary connexion. According to Hume, then, it is custom or habit that produces a feeling of determination that gives rise to the idea of necessary connexion, which is an "unobservable." In what follows, I argue that something somewhat similar occurs with respect to the notion of essence. I discuss a psychological explanation, namely Psychological Essentialism (PE), for modal intuitions, and argue that it is a better explanation for modal intuitions than the metaphysically extravagant ME. Here is how I plan to proceed. In Section 2, I discuss the explanandum, namely, modal intuitions. In Section 3, I discuss two potential explanations for modal intuitions, namely Metaphysical Essentialism (ME) and Psychological Essentialism (PE). In Section 4, I evaluate ME and PE relative to generally accepted criteria of selection. I conclude that PE is the better explanation among the two. If this is correct, then the fact that we have modal intuitions is not a strong reason to believe ME. 4 2. The explanandum: modal intuitions Consider the following examples of modal intuitions:  "We intuit that a particular bicycle which, in fact, came into existence made up of parts P1, P2, P3, . . .Pn, could not have come into existence made up of totally different parts. On the other hand, this bicycle could have come into existence with one of its parts different from the one it actually had. For example, our bicycle could have been constructed with a spoke other than one of its actual front-wheel spokes. (The bicyclebuilder says to his assistant, 'If you had ordered new spokes as I told you, this would have been a better bicycle'.)" (Chandler 1976: 106.)  "I think it is a fact about my cat, C. Louise, that she could not have been a banana. This is a fact about her. It is a fact about a particular protein that for it to exist it must include certain amino acids. This is a fact about it. More generally, it seems right to say that there are ways the world is independently of our descriptions or characterizations of the world, and these ways include facts about objects' natures" (Paul 2004: 170).  "Socrates' being human, for instance, seems more central or important to him-more 'of the essence' of him, as we say-than his being snub-nosed" (Gorman 2005: 276).  "however we characterize the essential/accidental property distinction, the characterization should not by itself rule out an otherwise intuitively compelling version of essentialism according to which Emma is essentially a dog" (Robertson 2008).  "being human (or being human if existent) is an essential property of mine" (Robertson 2008). 5  "I could not have been a credit card account" (Robertson 2008).  "(1a) It is part of John's essence that he is the son of his actual father. (2a) John's actual father is Fred. Therefore, (3a) it is part of John's essence that he is the son of Fred" (Bird 2008: 336).  "How could a person originating from different parents, from a totally different sperm and egg, be this very woman?" (Kripke 1972/1980: 113) (Cf. Hawthorne and Szabó Gendler 2000; Barnett 2005.) The last quotation from Kripke alludes to a version of ME that has come to be known as "origin essentialism," according to which "an object could not have had a radically different origin from the one it actually had" (Robertson 2008; cf. Kripke 1972/1980: 112-114). In what follows, I am concerned with essential properties, or essences, in general, regardless of whether origin, such as having originated from zygote z, turns out to be an essential property or not. 2 The aforementioned modal intuitions, then, are supposed to be the explanandum. That is to say, we need an account that, if true, would explain why we have these modal intuitions. In the next section, I consider two potential explanations for such modal intuitions: Metaphysical Essentialism (ME) and Psychological Essentialism (PE). 3 2 For more on origin essentialism, see Mackie (1974) and Salmon (1981). See also Mackie (2006: chaps. 7 and 8) on sortal essentialism, according to which "the essential properties of an individual involve the fact that it could not have belonged to a radically different kind from the kind (or kinds) to which it actually belongs" (Mackie 2006: 119). 3 For more on modal intuitions, see Levin (2011). 6 3. The explanans: ME vs. PE One explanation for our modal intuitions is that they track an unobservable reality. More explicitly, our modal intuitions tap into unobservable essences. Hence, when we intuit that Socrates is essentially human, our intuition is about a real thing, namely, the essence of being human and how it is an essential property of Socrates. This is Metaphysical Essentialism (ME), the view discussed in Section 1. Proponents of ME can then argue by Inference to the Best Explanation (IBE) (Psillos 2007) as follows: 1. We have modal intuitions. 2. The best explanation for (1) is ME. 3. No other hypothesis explains (1) as well as ME does. 4. Therefore, ME is probably true. The obvious question, of course, is whether premises (2) and (3) are true. Is ME truly the best explanation for our modal intuitions? Are there alternative explanations that explain our modal intuitions just as well as ME does? I think that ME is not the best explanation for our modal intuitions. Another explanation for our modal intuitions is Psychological Essentialism (PE). Contrary to ME, according to which our modal intuitions tap into an unobservable reality of essences, PE is the view that "essentialism is a reasoning heuristic that is readily available to both children and adults" (Gelman 2004: 404). According to PE, essence is "a human 7 construction rather than a perceived reality" (Gelman 2004: 405). As Bloom (2010) puts it, "We are natural-born essentialists." Proponents of PE can then argue by Inference to the Best Explanation (IBE) as follows: 1. We have modal intuitions. 2. The best explanation for (1) is PE. 3. No other hypothesis explains (1) as well as PE does. 4. Therefore, PE is probably true. Now the question is which explanation is better: ME or PE. To answer this question we need criteria for selecting the best explanation among competing explanations. Philosophers have offered the following key criteria of selection (Mizrahi 2012: 134): Unification: As a general rule of thumb, choose the explanation that explains the most and leaves the least unexplained things (see, e.g., Kitcher 1981). Coherence: As a general rule of thumb, choose the explanation that is consistent with background knowledge (see, e.g., Kosso 1992). Simplicity: As a general rule of thumb, choose the least complicated explanation, i.e., the one that posits the least causal sequences and entities, and that goes beyond the evidence the least (see, e.g., Sober 1988, 1994, and 1998). Testability: As a general rule of thumb, choose the explanation that yields independently testable predictions (see, e.g., Zahar 1973, Kitcher 1983, and Leplin 1997). 8 With these criteria of selection in hand, we can now judge whether ME or PE is the best explanation for modal intuitions. In other words, the question, for present purposes, is which of the inferences to the best explanation outlined above is cogent: the IBE for ME or the IBE for PE. 4. Evaluating ME and PE In terms of unification, it seems that both ME and PE, if true, would provide a fairly comprehensive account of modal intuitions. However, the problem is that ME seems to raise more questions than answers. As an explanation for modal intuitions, ME raises metaphysical questions about the nature of essences and their origin as well as epistemological questions about whether, and if so how, we gain access to the unobservable reality of essences. On the other hand, PE does not face these problems, since, if PE is true, essences are not real properties in the external world. Rather, they are heuristics or mental shortcuts that people use to make judgments and draw inferences quickly. In terms of coherence, proponents of ME could argue that ME is consistent with our background knowledge of unobservable entities in general. That is to say, postulating the existence of unobservable entities, such as electrons, is common practice in science. To that extent, essences are no different from electrons. In that respect, PE is not better than ME, for PE also postulates a mental shortcut that allows us to make judgments and draw inferences but that is unobservable, too. As unobservable entities, however, essences are rather unique and unfamiliar, whereas heuristics are much more common. For example, studies show that people 9 regularly use other heuristics or mental shortcuts, such as stereotypes (see, e.g., Bodenhausen 1990; Bastian and Haslam 2006). If PE is true, then essences are more like stereotypes than like electrons. In addition to consistency with background knowledge, what about internal consistency? Is ME internally coherent? Take origin essentialism, according to which a given human being could not have originated from a different zygote (Forbes 1986: 3-31). Since a zygote is the product of a sperm cell and an egg cell, and since each cell comes from a male and a female human being, respectively, it follows that each human being could not have originated from two different parents. Since this applies to every human being alive, it follows that at any given moment in the past, there must have been twice as many humans as at any given moment in the present. Even more problematic for origin essentialism is the following: 1. A human being H could not have originated from a different zygote. [Assumption for reductio] 2. If (1), then H must have originated from zygote z. 3. If (2), then H must have originated from H1 (from which the sperm cell that produced the zygote must have originated) and H2 (from which the egg cell that produced the zygote must have originated). 4. If (2), then H2 must have originated from H3 (from which the sperm cell that produced the zygote must have originated) and H4 (from which the egg cell that produced the zygote must have originated). 10 5. If (2), then H4 must have originated from H5 (from which the sperm cell that produced the zygote must have originated) and H6 (from which the egg cell that produced the zygote must have originated). 6. ... and so on, ad infinitum. 7. Therefore, it is not the case that a human being H could not have originated from a different zygote. If this reductio is sound, then ME commits one to the existence of not only queer entities, namely, essential properties, but also infinite regresses (of either humans or zygotes). In terms of simplicity, rather than being ontologically parsimonious (Sober 2001: 14), ME seems like a rather extravagant explanation, ontologically speaking, insofar as it postulates the existence of multiple entities, such as the essence of human, the essence of dog, and so on. Matters would be even worse for ME if we include also individual essences (cf. Mackie 2006: 19). 4 On the other hand, PE postulates the existence of a mental heuristic. In terms of testability, it seems that the only way to test ME is against our modal intuitions. Since our modal intuitions are the explanandum, however, we need independent evidence for ME, i.e., evidence that is independent of our modal intuitions. After all, one could argue that PE explains our modal intuitions just as well. So, is there an intuition-free way to test ME? I cannot think of one. (Of course, that does not necessarily mean there is no intuition-free way to test ME.) On the other hand, PE can be-and has been-tested in a variety of ways. For example, if PE is true, then we would expect that this heuristic would be available to children as 4 Incidentally, what is the essence of essence? See Schwartz (2009). 11 well. Several studies suggest that this is indeed the case (see, e.g., Medin and Ortony 1989; Gelman 2003). As Gelman (2004: 406) writes: both preschool children and adults from a variety of cultural contexts expect members of a category to be alike in non-obvious ways. They treat certain categories as having inductive potential, an innate basis, stable category membership, and sharp boundaries between contrasting categories. These beliefs are not the result of a detailed knowledge base, nor are they imparted directly by parents, although language might play an important indirect role. Instead, they appear early in childhood with relatively little direct prompting. Accordingly, as we would expect if PE were true, preschoolers use this heuristic without learning it directly. If the aforementioned considerations are correct, then PE is a better explanation for modal intuitions than ME. If this is correct, there is no need to postulate the existence of essences in order to explain our modal intuitions, for there is a much better explanation for why we have such intuitions. Consequently, the mere fact that we have modal intuitions is not a strong reason to believe that objects have essential properties. 5. Conclusion In this paper, I have argued that Psychological Essentialism (PE), the view that essences are a heuristic or mental shortcut, is a better explanation for modal intuitions than Metaphysical Essentialism (ME), the view that (at least some) objects have (at least some) essential properties. 12 PE is a superior explanation to ME in terms of unification, coherence, simplicity, and testability. These are criteria of selection that allow us to choose the best explanation among competing explanations. Judging ME and PE by these criteria yields a clear result: PE is a better explanation for modal intuitions than ME. If this is correct, then the mere fact that we have modal intuitions is not a strong reason to believe ME. References Barnett, David. 2005. "The Problem of Material Origins." Noûs 39 (3):529-540. Bastian, Brock and Haslam, Nick. 2006. "Psychological Essentialism and Stereotype Endorsement." Journal of Experimental Social Psychology 42 (2):228-235. Bird, Alexander. 2008. "Lowe on A Posteriori Essentialism." Analysis 68 (4):336-344. Bloom, Paul. 2010. "Why We Like What We Like." Observer 23 (8). Bodenhausen, V. G. 1990. "Stereotypes as Judgmental Heuristics: Evidence of Circadian Variations in Discrimination." Psychological Science 1 (5):319-322. Brogaard, Berit and Salerno, Joe. 2007. "A Counterfactual Account of Essence." The Reasoner 1 (4):4-5. Chandler, Hugh. 1976. "Plantinga and the Contingently Impossible." Analysis, 36 (2):106-109. 13 Forbes, Graeme. 1986. "In Defense of Absolute Essentialism." In P. French, T. Uehling, and H. Wettstein (Eds.), Midwest Studies in Philosophy XI: Studies in Essentialism (3-31). University of Minnesota Press. Gelman, S. A. 2003. The Essential Child: Origins of Essentialism in Everyday Thought. New York: Oxford University Press. Gelman, S. A. 2004. "Psychological Essentialism in Children." Trends in Cognitive Science 8 (9):404-409. Gorman, Michael. 2005. "The Essential and the Accidental." Ratio 18 (3):276-289. Hawthorne, John and Szabó Gendler, Tamar. (2000). "Origin Essentialism: The Arguments Reconsidered." Mind 109 (434):285-298. Hume, David. 1975. Enquiries concerning Human Understanding and concerning the Principles of Morals. L. A. Selby-Bigge (Ed.) Third edition with revised text and notes by P. H. Nidditch. Oxford: Oxford University Press. Hume, David. 1999. An Enquiry concerning Human Understanding. T. L. Beauchamp (Ed.). New York: Oxford University Press. Kitcher, Philip. 1981. "Explanatory Unification." Philosophy of Science 48 (4):507-531. Kitcher, Philip. 1983. Abusing Science: The Case Against Creationism. Cambridge, MA: The MIT Press. Kosso, Peter. 1992. Reading the Book of Nature: An Introduction to the Philosophy of Science. New York: Cambridge University Press. 14 Kripke, Saul. 1972/1980. Naming and Necessity. Cambridge, MA: Harvard University Press. Leplin, Jarrett. 1997. A Novel Defence of Scientific Realism. New York: Oxford University Press. Levin, Janet. 2011. "Reconstruing Modal Intuitions." Croatian Journal of Philosophy 11 (1):97112. Mackie, J. L. 1974. "De What Re Is De Re Modality?" Journal of Philosophy 71 (16):551-561. Mackie, Penelope. 2006. How Things Might Have Been: Individuals, Kinds, and Essential Properties. New York: Oxford University Press. Medin, D. L. and Ortony, Andrew. 1989. "Psychological Essentialism." In S. Vosniadou and A. Ortony (Eds.), Similarity and Analogical Reasoning (179-195). Cambridge: Cambridge University Press. Mizrahi, Moti. 2012. "Why the Ultimate Argument for Scientific Realism Ultimately Fails." Studies in History and Philosophy of Science 43 (1):132-138. Paul, L. A. 2004. "The Context of Essence." Australasian Journal of Philosophy 82 (1):170-184. Psillos, Stathis. (2007). "The Fine Structure of Inference to the Best Explanation." Philosophy and Phenomenological Research 74 (2):441-448. Robertson, Teresa. 2008. "Essential vs. Accidental Properties." In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), http://plato.stanford.edu/archives/fall2008/entries/essential-accidental/. Salmon, Nathan. 1981. Reference and Essence. Princeton, NJ: Princeton University Press. 15 Schwartz, S. P. 2009. "The Essence of Essence." Australasian Journal of Philosophy 87 (4):609623. Sober, Elliott. 1988. Reconstructing the Past: Parsimony, Evolution and Inference. Cambridge, MA: MIT Press. Sober, Elliott. 1994. "Let's Razor Ockham's Razor." In E. Sober (Ed.), From a Biological Point of View (136-157). Cambridge: Cambridge University Press. Sober, Elliott. 1998. "Simplicity (in scientific theories)." In E. Craig (Ed.), Routledge Encyclopedia of Philosophy. London: Routledge. http://www.rep.routledge.com/article/Q095SECT1. Sober, Elliott. 2001. "What is the Problem of Simplicity?" In A. Zellner, H. Keuzenkamp, and M. McAleer (Eds.), Simplicity, Inference, and Modeling: Keeping it Sophisticatedly Simple (1331). Cambridge: Cambridge University Press. Zahar, Elie. 1973. "Why Did Einstein's Programme Supersede Lorentz's?" (I) British Journal for the Philosophy of Science 24 (2):95-123. Zahar, Elie. 1973. "Why Did Einstein's Programme Supersede Lorentz's?" (II) British Journal for the Philosophy of Science 24 (3):223-262.