¹ Stearns and Hoekstra rightly insist that “The ideas of evolution have survived many controversies and tests and are now considered as reliable as any ideas in science.” Evolution: An Introduction (Oxford: Oxford University, 2005, 23)Google ScholarPubMed.

² It all began with Kripke's classic Naming and Necessity (Oxford: Blackwell, 1972)Google Scholar, although perhaps the laurel ought to go to Ruth Barcan Marcus – see her “Essentialism in Modal Logic” and “Essential Attribution” in Modalities: Philosophical Essays (Oxford: Oxford University Press, 1993)Google Scholar. See also Plantinga, Alvin, The Nature of Necessity (Oxford: Clarendon Press, 1974)Google Scholar; Putnam, Hilary, Mind, Language and Reality (Cambridge: Cambridge University, 1975)Google Scholar; Fine, Kit, “Postscript”, in Worlds, Times and Selves. Fine, and Prior, (eds) London: Duckworth, 1977)Google Scholar; Wiggins, David, Sameness and Substance (Oxford: Blackwell, 1980)Google Scholar; and Charles, David, Aristotle on Meaning and Essence (Oxford: Clarendon Press, 2000)Google Scholar. For a general overview of contemporary formulations of essentialist theses see Forbes, Graeme, “Essentialism”, in A Companion to the Philosophy of Language. Hale, and Wright, (eds). (Oxford: Blackwell, 1999, 515–533Google Scholar.

³ The resolution of such tensions is the bread and butter of philosophy. For an extended discussion of this understanding of the nature of philosophy see Boulter, Stephen, The Rediscovery of Common Sense Philosophy (Houndsmill: Palgrave Macmillan, 2007, ch. 1)Google Scholar; Rescher, Nicholas, Aporetics: Rational Deliberation in the Face of Inconsistency (Pittsburgh: Pittsburgh University Press, 2009)Google Scholar; and Hartmann, Nicolai, Grundzüge einer Metaphysik der Erkenntnis. 5th ed. (Berlin: W. de Gruyter, 1965)Google Scholar.

⁴ The literature on Aristotle's metaphysics is very extensive and extraordinarily sophisticated, and there is, unsurprisingly, room for rational debate regarding the details of his position. What I provide here, however, is relatively uncontroversial among Aristotle scholars. I follow the account given in Charles, op. cit. note 2.

⁵ It is not for nothing that Lawson-Tancred deemed Aristotle's “the received metaphysics of the Western world.” (In Aristotle, Metaphysics. Translation by Lawson-Tancred, (London: Penguin, 2004, xxiii)Google Scholar.

⁶ For further discussion see chapter 2 of Sterelny and Griffiths, Sex and Death: An Introduction to Philosophy of Biology (Chicago: University of Chicago Press, 1999)Google Scholar.

⁷ This argument is found in Mayr, Ernst, “Darwin and the evolutionary theory in biology”, Evolution and Anthropology: A centennial appraisal. Meggers, ed. (Washington DC: Anthropology Society of Washington, 1959)Google Scholar, and The Growth of Biological Thought (Cambridge Mass.: Belnap Press, 1982)Google Scholar. It is also expounded in Hull, David, “The effect of essentialism on taxonomy: two thousand years of stasis. Part 1”, Br. J. Philos. Sci., (1965), XVI: 1–18Google Scholar. See also Ghiselin, M.T., (1981) “Categories, life and thinking”, Behav. Brain Sci., (1981), 4: 269–283, 303–310Google Scholar.

⁸ This argument is also found in Mayr, op. cit. note 7.

⁹ That this latter point is required for the argument to have any force is not always spelled out explicitly, but John Dupré is clear on this. He doubts that descent is “even a candidate for an essential property” because this property is “purely relational”. The Disorder of Things: Metaphysical Foundations of the Disunity of Science (Cambridge, Mass: Harvard University Press, 1993, 56)Google Scholar.

¹⁰ For an expression of this argument see Okasha, Samir, “Darwinian Metaphysics: Species and the Question of Essentialism”, Synthese (2002), 131, 191–213CrossRefGoogle Scholar.

¹¹ See Sober, Eliot, “Evolution, Population Thinking, and Essentialism”, Phil. of Sci., (1980), 47, 350–83CrossRefGoogle Scholar.

¹² Op. cit., note 11, 370.

¹³ See Ereshefsky, M., “Eliminative Pluralism”, in The Philosophy of Biology. Hull, and Ruse, (eds). (Oxford University Press, 1998)Google Scholar.

¹⁴ See Bernier, R., “The Species as an Individual: Facing Essentialism”, Systematic Zoology Vol. 33, No. 4, (1984), 467CrossRefGoogle Scholar.

¹⁵ “Logical Difference and Biological Difference: the Unity of Aristotle's Thought”, in Philosophical Issues in Aristotle's Biology, Gotthelf, and Lennox, (eds). (Cambridge: Cambridge University Press, 1987)CrossRefGoogle Scholar.

¹⁶ Aristotle's de Partibus Animalium and De Generatione Animalium I (Oxford: Clarendon Press, 1972)Google Scholar.

¹⁷ “Material and Formal Natures in Aristotle's de Partibus Animalium” and “Kinds, Forms of Kinds, and the More and the Less in Aristotle's Biology”, in Aristotle's Philosophy of Biology (Cambridge: Cambridge University Press, 2001)Google Scholar.

¹⁸ “Evolutionary Essentialism”, Brit. J. Phil. Sci. 57 (2006), 431Google ScholarPubMed.

¹⁹ Op. cit., note 18, 426.

²⁰ Of course there are good grounds for maintaining that organisms are ontologically irreducible. Mayr himself goes to considerable lengths to establish precisely this point, identifying eight characteristics of living organisms that have no parallel in the inanimate world (op. cit. note 7, 1982, 36–59). And even those who expect that such a reduction will be effected eventually acknowledge that such a reduction would require significant changes to our understanding of physics and chemistry, and most likely include a commitment to downward causation. For further discussion see Keller, E.F., “It is Possible to Reduce Biological Explanations to Explanations in Chemistry and/or Physics”, in Contemporary Debates in Philosophy of Biology. Ayala, and Arp, (eds). (Oxford: Wiley-Blackwell, 2010, 19–31)Google Scholar, and Dupre, John, “It is not Possible to Reduce Biological Explanations to Explanations in Chemistry and/or Physics”, in Contemporary Debates in Philosophy of Biology. Ayala, and Arp, (eds). (Oxford: Wiley-Blackwell, 2010, 32–47)Google Scholar.

²¹ Of course these arguments are redundant for those who already accept that species are natural groups, the foregoing reflections on the problem of change being sufficient to force essentialism.

²² That is, ancestral species A does not continue to exist in virtue of metamorphing into species B or C. Does this conflate sortal persistence conditions with diachronic identity conditions? Some metaphysicians want to distinguish the question “Under what conditions can x remain the kind of thing x currently is?” from “Under what conditions can x remain x?” Those who wish to preserve this distinction are motivated by the concern to allow for the possibility of metamorphosis of the sort associated with classical mythology, i.e., where Lucius, say, begins life as a human being, is transformed into an ass, and is ultimately returned to human form, all the while remaining Lucius. I think such scruples can be set aside here. For one, many will wonder whether the myths of metamorphosis are in fact fully intelligible (could Lucius really be an ass and remain Lucius?). For those whose intuitions prevent them from embracing metamorphosis as a genuine possibility sortal persistence conditions just are diachronic identity conditions because the identity of x is determined by x's sortal. But these considerations can be set aside in the current context because no evolutionary biologist believes that speciation events are cases of metamorphosis.

²³ The crucial point about adaptations is that they are features or characters that at some point in their phylogenetic history were derived. That is, for a trait to be an adaptation there must have been at one stage of its history a transition from the ancestral to the derived state. This does not mean that this trait ceases to be an adaptation if it is subsequently passed on without modification to another species after further cleavage in the lineage. Adaptations can be, and often are, ancestral traits with respect to a particular set of species, say species C, D and E, where C is a daughter species of ancestral species A, and D and E are daughter species of C.

²⁴ That phylogenetic trees are genuinely illuminating is assumed whenever they are employed in biochemistry, immunology, ecology, genetics, ethology, biogeography and stratigraphy. This assumption also underwrites a major methodological procedure in biology. Comparative analyses are only illuminating if the classification of the items being compared and their relationships are assumed to be accurate reflections of mind-independent biological reality. Thus phylogentic trees taken to represent mind-independent biological reality are necessary to comparative anatomy, comparative physiology, and comparative psychology. It is worth noting in this regard that realism about species is advocated by Darwin himself in the famous thirteenth chapter of On the Origin of Species. “All the foregoing rules and aids and difficulties in classification are explained, if I do not greatly deceive myself, on the view that the natural system is founded on descent with modification; that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parent, and in so far, all true classification is genealogical; that community of descent is the hidden bond which naturalists have been unconsciously seeking, and not some unknown plan of creation, or the enunciation of general propositions, and the putting together and separating objects more or less alike”. On the Origin of Species. In From So Simple a Beginning. The Four Great Books of Charles Darwin. Wilson, E.O. (ed.). (New York: W.W. Norton, 2006, 717)Google Scholar. If there is any question about how one is to read these lines, Darwin underlines his realism with the claim that “This classification is evidently not arbitrary like the grouping of the stars in constellations” (op. cit., 711).

²⁵ See Stearns and Hoekstra for further discussion (op. cit. note 1, 137).

²⁶ Op. cit., note 9, 55.

²⁷ Developmental Plasticity and Evolution (USA: Oxford University Press, 2003, 528)Google ScholarPubMed.

²⁸ Op. cit., note 27, 24.

²⁹ The Shape of Life: Genes, Development and the Evolution of Animal Form (Chicago: University of Chicago Press, 1996, 31)Google Scholar.

³⁰ Op. cit., note 29, 360.

³¹ Some metaphysicians are willing to allow two objects to occupy the same space simultaneously. The standard example being a lump of clay and a vase composed of the clay. When the vase breaks the vase no longer exists but the clay remains, which means the vase was not the clay, and the clay was not the vase. One way to understand this is to maintain that the clay and the vase are two distinct objects which overlapped at one stage of their respective careers. But no one to my knowledge believes that this model can be extended to embrace the overlapping of two or more distinct organisms.