The persisting problem of the ship of Theseus

Hylemorphism is the view that objects are-in some sense-compounds of matter and form. Principle-based hylemorphism is the view that forms are principles of unity. In this paper I want to rise a challenge to contemporary versions of principle-based hylemorphism. The challenge emerges from two assumptions that are commonly acknowledged by principle-based hylemorphists. First, each object has, associated with its sort, certain persistence conditions. Second, for an object to be of a particular sort is for it to have a particular (kind of) form. It follows that there is an intimate relationship between an object's form and its persistence conditions. The challenge for the principle-based hylemorphist is to provide a satisfactory explanation of this relationship. What it needs to answer this challenge depends in part on what persistence conditions are. According to a common understanding, persistence conditions are something like conditions of temporal composition. If this understanding were correct, the standard principle-based hylemorphist could meet the challenge quite easily. I argue, however, that this understanding is not correct. Persistence conditions are not conditions of temporal composition, but conditions of staying in existence. It turns out that, with this understanding in place, standard versions of principle-based hylemorphism are incapable of explaining persistence conditions. However, instead of rejecting principle-based hylemorphism, I suggest a modification that allows to give the required explanation. We should distinguish between two layers of forms: a principle of existence and a principle of persistence. While the former is associated with the object's existence conditions, the latter provides the object with its persistence conditions.

2011

In antiquity, the problem of persistence through time is usually associated with certain puzzles or paradoxes, such as the Ship of Theseus and Epicharmus’ Growing Argument, which call into question the assumption that an enduring entity can gain and shed properties while still remaining numerically the same. Although Aristotle gives ample attention in the Physics to the Zenonian paradoxes of motion, he makes no mention of puzzles that focus mainly on problems of persistence, except for one brief reference in Physics Book 4, chapter 11. The reference occurs in a discussion of time, where Aristotle tries to account for the fact that ‘the now’ is in a way always the same and in a way always different. The puzzle in question is alluded to when he claims at 219b18-22 that a moving thing like a stone has this same feature:

Philosophy of Logic and Mathematics, eds. Mras, Weingartner, and Ritter. De Gruyter, 2019

Properties and relations in general have a certain degree of invariance, and some types of properties/relations have a stronger degree of invariance than others. In this paper I will show how the degrees of invariance of different types of properties are associated with, and explain, the modal force of the laws governing them. This explains differences in the modal force of laws/principles of different disciplines, starting with logic and mathematics and proceeding to physics and biology.

In this paper I investigate the thought experiment of “The Ship of Theseus” in an attempt to compose an alternative theory, within the debate of persistence, which is capable of accounting for object identity. This I do by first using the unique bundle theory of universals to show how the problem presented by the thought experiment is in fact no problem at all, according to an analysis of the object’s content. However, according to our common sense, these problems persist and are unexplainable by the dominant theories of continuity of form and identity of original parts. After showing how the two theories are unsuccessful in explaining the problem, and only serve to bring more problems into the debate, I introduce the notion of an object’s role as grounding our common sense notion of identity. After clarifying the notion of a role as the strictly dependent continuing potential functions of an object I show how this new role-theory is capable of solving the problem introduced by the original thought experiment and also the mentioned problems introduced by the continuity of form and identity of original parts theories. In conclusion I show how the role-theory is capable of avoiding the problem of an object’s “history” that no other theory can explain.

Canadian Journal of Philosophy, 2003

Our topic is the ontology and persistence conditions of material objects. One widely held doctrine is that identity-over-time has causal commitments. Another is that identity-over-time is just identity (simpliciter) as it relates one object that exists at two times. We believe that a tension exists between these two apparently sensible positions: very roughly, if identity is the primary conceptual component of identity-over-time and—as is plausible—identity is noncausal, then the conceptual origins of the causal commitments of identity-over-time become a mystery. We will begin by formulating the two widely held doctrines and our puzzle more fully and more carefully. Then, the remainder of the paper will be devoted to analyzing views one might adopt that could minimize the tension.

The Turning Points of the New Phenomenological Era, 1991

2008

"The last remnant of physical objectivity of space-time" is disclosed in the case of a continuous family of spatially non-compact models of general relativity (GR). The physical individuation of point-events is furnished by the intrinsic degrees of freedom of the gravitational field, (viz, the Dirac observables) that represent-as it were-the ontic part of the metric field. The physical role of the epistemic part (viz. the gauge variables) is likewise clarified as emboding the unavoidable noninertial aspects of GR. At the end the philosophical import of the Hole Argument is substantially weakened and in fact the Argument itself dissolved , while a specific four-dimensional holistic and structuralist view of space-time, (called point-structuralism), emerges, including elements common to the tradition of both substantivalism and relationism. The observables of our models undergo real temporal change: this gives new evidence to the fact that statements like the frozen-time character of evolution, as other ontological claims about GR, are model dependent.

Between Logic and Reality, 2012

A theory of temporal mereology is formulated in which both the principles of Existence and of Uniqueness of Composition hold. The theory is consistent both with a three-dimensionalist ontology and with the change of parts, that is, with the view that at least one object has distinct parts at distinct times. Some interesting consequences of the theory and the change of parts, taken as an axiom, are proven. It is usually held that certain well known ontological puzzles must be solved either by adopting a four-dimensionalist ontology or by restricting some mereological principles. Here a solution to those puzzles is stated, which allows to keep all mereological principles in their generality, without adopting a four-dimensionalist ontology. The solution is achieved by denying the persistence of some of the entities involved, along the 'Chrysippean' lines advocated by M. Burke and M. Rea. Although good reasons for this move are provided, some problems of the solution are also highlighted and tentatively answered.

Philosophy of Science, 2000

The nature of persistence over time has been intensely debated in contemporary metaphysics. The two opposite views are widely known as "endurantism" (or "three-dimensionalism") and "perdurantism" ("four-dimensionalism"). According to the former, objects are extended in three spatial dimensions and persist through time by being wholly present at any moment at which they exist. On the rival account, objects are extended both in space and time and persist by having "temporal parts," no part being present at more than one time.