Essence and Accident

Socrates was a philosopher and was snub-nosed. He could have been neither: he might have taken up carpentry, and a different nose would not have made him someone else. But could he have been a poached egg? Could he have failed to be human, or to be the child of his actual parents?

The distinction between what a thing is essentially and what it is accidentally is among the oldest in metaphysics, and it was widely regarded as unintelligible for much of the twentieth century before returning to the centre of the subject.

The modal analysis

The standard modern account explains essence in terms of necessity. A property $F$ is essential to $x$ just in case $x$ must have it if it exists at all:

$$F\text{ is essential to }x{=}_{\mathrm{df}}\square (\exists y(y=x)\to Fx)$$

Everything else it has is accidental. The analysis is attractively economical: given a possible-worlds semantics for $\square$, essence requires no new primitive, only quantification over worlds.

Kripke's Naming and Necessity supplied the examples that made the notion respectable again:

• Origin essentialism. This table could not have been made from a different block of wood. A qualitatively identical table made from other material would be a different table.
• Kind essentialism. Socrates could not have been a poached egg; a thing cannot change its fundamental kind across worlds.
• The necessity of identity, discussed on the identity page: identities among rigid designators hold in every world.

The last two are necessary a posteriori, which is what made the package philosophically explosive: necessity had been assumed to be the province of the a priori.

Fine's counterexamples

Kit Fine's "Essence and Modality" (1994) argued that the modal analysis is extensionally wrong, and the argument is one of the cleanest in recent metaphysics. Consider Socrates and his singleton set $\{\mathrm{Socrates}\}$.

• Necessarily, if Socrates exists, he is a member of $\{\mathrm{Socrates}\}$. So by the modal analysis, being a member of $\{\mathrm{Socrates}\}$ is essential to Socrates.
• But it is not. Nothing about what Socrates is — nothing in any account of his nature — involves that set. The set has him as a member essentially; he does not have it as a container essentially. The dependence runs one way, and the modal analysis cannot see the asymmetry, because necessity is symmetric here.

Further cases make the point sharper. Necessarily, if Socrates exists, $2+2=4$; so on the analysis, being such that $2+2=4$ is essential to Socrates. Necessarily he is distinct from the Eiffel Tower. Necessarily he is a member of every set containing him. All of these come out essential, and none of them is any part of what he is.

The diagnosis: essence is not a modal notion at all. It is a matter of real definition — of what a thing is, in the sense the definition of a term captures for the term. Fine's proposal reverses the order of explanation: essence is primitive, and necessity is defined from it. The necessary truths are those that flow from the natures of things.

This reversal has consequences beyond the local dispute. It gives a source for modality that does not depend on possible worlds, which matters to anyone who finds that ontology extravagant; and it makes essence the fundamental notion in a family that includes ontological dependence and grounding, which are the growth areas of contemporary metaphysics.

Quine's objection

The tradition Fine was reviving had been dismissed by Quine, whose objection to de re modality is worth stating because the reply to it clarifies what essentialism claims.

Consider a man who is both a mathematician and a cyclist. Qua mathematician he is necessarily rational and contingently two-legged; qua cyclist he is necessarily two-legged and contingently rational. So whether a property is essential appears to depend on how the object is described — and if so, there is no fact about what the object is essentially, only facts about descriptions. Quine concluded that de re modality is unintelligible and that essentialism is "invidious."

The essentialist reply is that the argument assumes what it purports to show. Essentialism is precisely the thesis that objects have their essential properties absolutely, not relative to a description. The man is rational essentially and two-legged accidentally, full stop; "necessarily two-legged qua cyclist" is not a claim about him but about the concept cyclist, which analytically involves having legs. Once de re and de dicto necessity are distinguished, the appearance of relativity vanishes.

Whether that reply is adequate depends on whether de re modality can be given a semantics that does not secretly go by way of descriptions — which is what possible-worlds semantics with rigid designation was designed to supply, and why Kripke's work rather than any direct refutation is what ended the Quinean consensus.

Sortals and identity conditions

A practical form of essentialism runs through the rest of this section. A sortal term — statue, lump, person, ship — carries with it conditions for counting and for persistence: what it takes to be one of these, and what changes one can survive.

This is why the statue and the clay puzzle is a puzzle. The two objects differ in modal properties precisely because they fall under different sortals with different persistence conditions, and the grounding problem is the demand to say what makes the sortal apply, given identical matter.

It is also why the Ship of Theseus can look like a verbal dispute. If the persistence conditions associated with "ship" are not determinate enough to settle the case, then nothing about the world is left unsettled when the question goes unanswered — a diagnosis with the same shape as the deflationary treatment of ontological disputes generally.

Where essence sits

Essence belongs to the category question: what a thing essentially is fixes the kind it belongs to, and kinds are what a category scheme sorts. It also connects the section's inventory disputes to its formal apparatus, since modal claims about objects are the standard evidence for their distinctness.

The Finean reversal is the item with the widest consequences. If essence is prior to modality, then a good deal of what recent metaphysics did with possible worlds should have been done with real definitions instead — and the notions of dependence, grounding, and fundamentality that dominate current work are its descendants.

The final page of this folder takes essentialism from individuals to kinds: are there natural kinds, and do the sciences discover them? The consequences of the reversal for modality itself are taken up under modality and essence.