1. The problem of change lies at the heart of a family of metaphysical approaches that may be conveniently subsumed under the label 'persistence theory'. We generally believe that objects persist through their changes. To persist through time, it is assumed, is to preserve self-identity through change. In that case, if objects persist through time while undergoing change, how is it possible to explicate the preservation of self-identity through change? Since change may be defined as instantiating incompatible properties in one object at different times, the clarification and explication of persistence must reconcile the concomitance of change and identity.

The premise underlying the variety of metaphysical treatments included in the anthology may be expressed as the assumption that objects persist through time. On this premise, the problem turns into finding an explanation that may be given to the intuitively ascertainable fact of the persistence of objects: How is it possible to account for the fact that objects persist by preserving their self-identity while undergoing temporal change in the sense of having incompatible properties at different times?

2. One way of approaching an answer stems from the Quinean motive displayed in the classic essay "Identity, Ostension, and Hypostasis" (Quine 1950) which frames persistence through time in terms of temporal parts of objects, denouncing thereby the foundation for any identity perseverance across the progression of temporal parts. If we conceive the temporal existence of an object in analogy with the spatial extension of (say) a road, we may designate an early temporal part and a later temporal part of the object as well as a lower spatial part and a higher spatial part of the same object. In this we may proclaim that the object is constituted by a succession of temporal parts of stages without contending that self-identity is preserved from one temporal stage to the next. The temporal parts instantiate properties, which as such may change from one temporal stage to the next. Since the object is conceived to be wholly present at each stage, and each stage is distinct from any other stage, different properties instantiated in different stages entail no incompatibility. 

This understanding of the temporal mereology of objects conceives of persistence in terms of endurance. The object persists across time by having different temporal parts, which as such instantiate different properties without invoking incompatibility, since each stage is distinct from any other stage of the temporal succession of object. The enduring object may be said to be "wholly present at each moment of its existence" (Hanchliff "The Puzzle of Change" 1996), instantiating different properties at different times without inflicting any kind of incompatibility. Of course, the immediate problem is that the identity of the object dissolves, since endurance, according to some commentators (Hawley, Kurtz, Quine, Sider, Hanchliff), cannot sustain identity across stages.

3. The opposing camp promotes the idea that objects persist by instantiating different stages or temporal parts at different times, without holding that any distinct part constitutes the whole object. A young man changes into an old man by being young at certain temporal parts and by being old at certain other temporal parts of his existence. This conception frames the identity of the man by means of the world-line of the man which as such consists of the sum of the temporal parts of the man, precisely as the body of the man consists of the sum of the spatial parts of the man. The man persists through change in virtue of being constituted by temporal parts which as such instantiate different properties at different times. The problem of perdurance is evident by the observation that change "requires one and the same changing thing to have both the incompatible properties concerned" (Mellor: 289, excerpt from Real Time). Again, if the young man and the old man merely constitute distinct temporal parts of the man — and not the whole man himself — we can hardly claim to have resolved the problem of how it is possible that an object instantiates incompatible properties at different times. In analogy, we can hardly claim that the road instantiates incompatible properties by being even at one spatial part and uneven at another spatial part of the road. It must be claimed that the whole road is even and uneven in order to elicit the assumed incompatibility of properties.

4. Many intriguing interpretations of the mereological character of temporal ontology are presented in this collection of essays which primarily seeks the attention of post-undergraduate analytic researchers. As such, Persistence: Contemporary Readings provides an elaboration of certain issues within the analytic metaphysics of time which is narrow in content and deep in exploration. Narrow in content in the sense that non-analytic readers will hardly make their way through more than a few paragraphs before giving up the effort. Deep in exploration in the sense that the issues discussed are treated thoroughly from a number of angles and theoretical positions.

The anthology is nicely organized in dialectic order, exhibiting papers for and against a number of central metaphysical conceptions, such as the notion of identity, different modal-temporal ontologies, interpretation of temporal mereology, statements of eternalism vs. presentism, specifications of semantic and metaphysical conditions for property instantiation, and related issues. Some of the papers — Sider: "Four-Dimensionalism", "All the World's Is a Stage"; Thomson: "Parthood and Identity Across Time",  van Inwagen: "Four-dimensional objects"; Balashov: "Persistence and Space-Time: Philosophical Lessons of the Pole and Barn" — presuppose familiarity with mathematical logic and contemporary modal epistemology, whereas other pieces (the excerpt from Quine and Taylor's significant paper "Spatial and Temporal Analogies and the Concept of Identity" (1955)) may be fruitfully read also by researchers from outside the analytic field.

5. It deserves to be mentioned that the theoretical profile of the papers to a large extent originates in the methodology and problem-setting inherited from the work of David Lewis, who is represented by three pieces. Although many of the contributions provide self-contained introductions as to the problematics associated with the notion of persistence (for instance, Forbes, Hanchliff, Johnston, Kurtz, Markossian, Sider), the anthology would have benefited by the inclusion of a paper from a 'meta-persistence' point of view which aligns persistence theory within the broader vistas of the philosophy of time, for instance those related to issues pertaining to Kantian, Husserlian and Wittgensteinean styles of investigation. Since the treatments of persistence rely heavily on the understanding of the modal-temporal ontology deriving from realist-materialist quarters (Smart, Lewis, Armstrong, and other brilliant writers), the whole approach towards temporality and change may be challenged on the score of intelligibility: What is actually resolved by the proposed definitions of perdurance and endurance? How is it possible to illuminate actual experience by means of the logical exercises in metaphysical extrapolation? On this score, the selected essays provide excellent starting-points for such investigation.

©  2007 Kyriakos Theodoridis

Kyriakos Theodoridis, Ph.D. theoretical philosophy, Independent Scholar, kyriakos.theodoridis@mah.se

Categories: Philosophical