Allan Gibbard on Contingent Identity
Our author tries to understand when a lump of clay and a statue made from this lump are identical. There are situations in which they are not, if the clay and the statue are generated or corrupt at different times. But: “I make a clay statue of the infant Goliath in two pieces, one part above the waist and the other part below the waste. Once I finish the two halves, I stick them together, thereby bringing into existence simultaneously a new piece of clay and a new statue. A day later I smash the statue, thereby bringing to an end both statue and piece of clay. The statue and piece of clay persisted during exactly the same period of time.” (Metaphysics: An Anthology, 102) Gibbard in this part of the paper thinks of the statue as form-in-matter: “By a statue here, I do not mean a shape of which there could be more than one token, but a concrete particular thing… A clay statue consists of a piece of clay in a specific shape.” (101) And he thinks of the clay as matter-having-a-particular-form: “They began at the same time, and on any usual account, they had the same shape, location, color, and so forth at each instant in their history; everything that happened to the one happened to the other…” (102) Obviously, the two are one and the same thing, even if different aspects of them are emphasized in their definitions.
But later on Gibbard contradicts himself: “Take a possible world in which I squeeze Lumpl into a ball, and suppose all the molecules involved are clearly identified. There are still two distinct things in that world, the statue Goliath which I destroy by squeezing, and the piece of clay Lumpl which survives the squeezing.” (107) If Lumpl survives the squeezing, then its particular shape cannot be its essential but must inevitably be an accidental property. But the statue’s exact shape is essential to it. If it were remade into a statue of David, then the old statue would cease to exist and a new statue would come into being. What our author calls “persistence criteria” for the two things differ. Goliath’s persistence criteria are more stringent that Lumpl’s. Hence the two properties are not identical (the property “humanoid shape” of both Goliath and Lumpl itself has a property with different values, viz., its modality: for Goliath it is essential or necessary, for Lumpl, merely contingent), and so Lumpl and Goliath are numerically distinct.
Gibbard’s case is that given that the two are identical in the actual world, and that both are rigid designatiors (relative to a sortal: one of them names the same Goliath in each possible world or the the same Lumpl in each possible world, but it is meaningless to say, Gibbard asserts, that they name the same thing in each world), they fail to be identical in the possible world in which the statue is squeezed into a ball. I, however, would describe the situation differently. We don’t need to invoke possible worlds and counterfactuals to show that this is so. Lumpl has the power to endure even if squeezed into a ball. Goliath does not have this power. Consequently, their essences differ. Therefore, this is not a case of contingent identity, because it is not a case of identity at all. The two things are not the same even in the actual world.
It may be objected that the meaning of the term “power” or “disposition” can only be understood in terms of possible worlds. I don’t think that’s true. Consider sentences of the form Sx → (Fx ↔ Bx), where S is an observation term describing a test condition, F is a theoretical term, and B is an observation term describing an outcome of the test. An example of this is defining the term “fragile.” One apparent possibility is to write Fx ↔ (Sx → Bx) or “something if fragile iff if you strike it, then it breaks.” But what if you never strike it? Then Fx will be true, since falsehood logically implies anything. Hence the original definition which reads “if you strike something, then it is fragile iff it breaks.” This avoids the problem of the first definition by making Fx undefined unless x is actually struck. Here we only have material conditionals. Second, it could be said that the modality of the form is a queer property and is precisely the reason for the contingency of identity between Goliath and Lumpl. For if Lumpl is matter-having-a-particular-form, then in the actual world Lumpl maintains that form. Maybe, but would we in ordinary language say after the statue is broken that Goliath and Lumpl were two names for the same thing?
Finally, a puzzle and a request for help. Gibbard distinguishes between individuals or concrete objects and “individual concepts.” At first glance this seems like a terminological refinement: concrete things exist only in the actual world (which is why he later says that concrete things have no de re properties nor dispositions, both of which might require them to exist in possible worlds, as well), while concepts exist in possible worlds. Is it because a thing cannot “exist” in a world that “does not exist”? But what does it have to do with the author’s main thesis?