Persistence: Endurantism vs. Perdurantism

A chair exists today and existed yesterday; a person is the same person across decades of change. How does a single object manage to exist through time — to be one thing present at many moments? This is the problem of persistence, and the two great answers divide the metaphysics of objects along the same fault line that the presentism/eternalism debate divides the metaphysics of time. The endurantist says objects are wholly present at each moment they exist; the perdurantist says objects persist by having distinct temporal parts at each moment, no one of which is the whole object. The dispute connects directly to the nature of time: four-dimensionalism about objects sits naturally with eternalism and the block universe, while endurantism is the traditional partner of presentism.

This page sets out the positions, the argument that most sharply divides them (temporary intrinsics), and the links to time and relativity.

The two theories of persistence

• Endurantism (three-dimensionalism). An object persists by enduring: it is wholly present at every moment of its existence. The whole chair — all of it — exists today, and the numerically same whole chair existed yesterday. Objects are three-dimensional; they lack temporal parts as they lack spatial "wholes" that are only partly there. Persistence is identity through time: one and the same complete entity, showing up entire at each moment.
• Perdurantism (four-dimensionalism). An object persists by perduring: it is a four-dimensional "spacetime worm" extended through time as well as space, and it is present at a moment only by having a temporal part — a momentary time-slice — located there. The whole object is the sum of all its temporal parts, past, present, and future; what exists "today" is just today's slice, a proper part of the whole. Just as a road is not wholly present at each town it passes through but has a spatial part there, an object is not wholly present at each moment but has a temporal part there.

A close cousin of perdurantism is the stage view (exdurantism, Sider): the everyday object is identified with the momentary stage itself, and persistence is analysed via a counterpart relation among stages ("the person yesterday" is a distinct but suitably related stage). Perdurantism and the stage view are the two forms of four-dimensionalism.

The argument from temporary intrinsics

The most influential argument in the debate is David Lewis's problem of temporary intrinsics. Objects change their intrinsic properties over time: a person is straight (standing) in the morning and bent (sitting) in the evening. "Straight" and "bent" are intrinsic shapes — properties a thing has in virtue of how it is, not how it relates to other things — and they are incompatible. So how can one object have both?

• The endurantist's difficulty. If the very same, wholly present object exists in the morning and in the evening, and it is straight in the morning and bent in the evening, then one and the same thing has incompatible intrinsic properties — a contradiction. The endurantist must qualify this, and the options all have costs:
  • Relativise the properties to times — the object is "straight-at-$t_1$" and "bent-at-$t_2$." But then shapes are no longer intrinsic (they become relations to times), which Lewis found incredible: my shape now is not a relation I bear to a moment.
  • Relativise the having (adverbialism) — the object has straightness $t_1$-ly and bentness $t_2$-ly. Critics complain this obscurely modifies "instantiation" without saying what that means.
  • Presentism — only the present exists, so the object is just bent (now), and was straight; there is no single time at which it has both, so no contradiction. This is the endurantist's cleanest escape, but it buys persistence at the price of accepting presentism, with all that view's truthmaker and relativity problems.
• The perdurantist's easy answer. There is no contradiction because the incompatible properties belong to different temporal parts: the morning-part is (simply, intrinsically) straight and the evening-part is (simply, intrinsically) bent, just as a poker can be hot at one end and cold at the other. Different parts, different properties — no single thing has both. Lewis took this to be a decisive advantage of perdurantism.

The endurantist replies that temporal parts are themselves a strange and unmotivated ontology — I do not seem to be composed of momentary slices the way a road is composed of stretches — and that the presentist or adverbialist responses, whatever their costs, are less revisionary than slicing every persisting thing into an infinity of ephemeral parts.

The link to time and relativity

The persistence debate is not settled by, but is deeply entangled with, the nature of time:

• Perdurantism ↔ eternalism/block universe. Temporal parts are most at home if all times are equally real: the four-dimensional worm needs its past and future slices to exist to be their sum. So perdurantism fits eternalism and the block universe hand in glove — indeed special relativity, by treating time as a fourth dimension on a par with space, makes the "spacetime worm" a natural object, and many take relativity to favour four-dimensionalism.
• Endurantism ↔ presentism. Endurantism's cleanest response to temporary intrinsics is presentism, and endurance — the whole object, present now — coheres with a metaphysics in which only the present is real.

Because relativity pressures presentism (no global "now"), it thereby indirectly pressures the presentist form of endurantism, and lends support to the perdurantist–eternalist package. This is one of the clearest cases in metaphysics where a view about objects is shaped by physics via a view about time.

Where this sits

Persistence is where the temporal question reaches into the metaphysics of ordinary objects. It inherits its options from presentism and eternalism and is pulled by the same relativistic considerations toward the four-dimensional block universe; it also connects to supersubstantivalism, whose identification of objects with spacetime regions is naturally read in a four-dimensionalist key. The final page of this subfolder pushes the metaphysics of time to its limit — time travel, where the coherence of a persisting object visiting its own past is put to the test.