Reconciling Perdurantism with A-Theory: A Spacetime-Constructivist Approach — Epoche C1
Two Questions: How Time Is, and How Things Persist Two separable questions organise the metaphysics of time, and the argument of this essay depends on keeping them separate. The first asks what time itself is like. The vocabulary here descends from J. M. E. McTaggart's 1908 paper "The Unreality of Time", which distinguished two ways of ordering events: the A-series , which ranks them as past, present or future — positions that constantly change, as tomorrow's meeting becomes today's and then yesterday's — and the B-series , which ranks them only as earlier than, simultaneous with, or later than one another — relations that never change, since the battle of Plassey is earlier than the battle of Waterloo eternally. An A-theorist holds that the A-series is fundamental: tense is a feature of reality itself, time genuinely passes, and there is an objective fact about which moment is now . In its strongest form, presentism , only the present exists — dinosaurs and lunar colonies alike are simply not part of what there is. A B-theorist holds instead that reality is a four-dimensional block in which all times are equally real and "now" is merely indexical, picking out the time of utterance just as "here" picks out the place of utterance; this view is also called eternalism . The second question asks how ordinary objects persist through time. An endurantist says a persisting object is wholly present at every moment of its existence: the whole of you sat at breakfast, and the whole of you sits here now. A perdurantist says a persisting object is spread out in time the way a road is spread out in space: it has temporal parts — momentary or short-lived stages — and no more than one of them exists at any one time, just as no more than one milestone of the road stands at any one point. On this view the persisting object is the mereological sum of its temporal parts, where mereology is simply the formal theory of parts and wholes, and a sum (or fusion) of some things is the whole that they compose, as the slices compose the loaf. David Lewis is the great modern champion of perdurantism, and his master argument for it, given in On the Plurality of Worlds (1986), is the problem of temporary intrinsics . An intrinsic property is one a thing has just in virtue of how it itself is — shape, mass — as opposed to relational properties like being an uncle. Objects change their intrinsic properties: I am bent while sitting, straight while standing. But nothing can be both bent and straight, so how can one thing have both properties? Lewis canvassed three answers. First, make the properties covertly relational — I bear bent-at to breakfast-time and straight-at to noon — which he rejected because shape seems intrinsic, not a relation to a time. Second, adopt presentism — only my present shape exists, so no contradiction ever arises — which he rejected because it denies the reality of other times, and with it, he thought, the plain truth that we have pasts and futures. Third, his own answer: the bent thing and the straight thing are numerically different temporal parts of me, and different things may differ in shape without contradiction. Because Lewis dismissed the presentist escape at exactly this juncture, his perdurantism is commonly seen as inextricably wedded to the B-theoretic block, in which all the temporal parts tenselessly coexist. This essay argues that the marriage, though historically real, is not metaphysically forced — much as, in the layered narratives of South Asian storytelling, a tale within a tale reveals a truth the framing tale had concealed. One point of honesty at the outset: the "spacetime-constructivist" reading developed below is a revisionary proposal about what Lewis's machinery can accommodate, not a claim about what Lewis himself believed; he was an avowed eternalist, and the label is this essay's, not his. The Incompatibility Objection The traditional objection to combining perdurantism with a presentist A-theory can now be stated exactly. Perdurantism identifies the persisting Banyan tree with the sum of temporal parts located at many times — the 1850 part sitting in 1850 and having its shape and size there, the 2150 part in 2150. Presentism says that only present things exist. But a sum cannot outrun its parts: if the sapling-part of 1850 and the towering-part of 2150 do not exist, there is nothing for the alleged sum to be a sum of , beyond the single part that exists now. The persisting object collapses into its present slice, and perdurantism — the doctrine that the object is more than any one slice — dissolves. This is why the combination is standardly treated as incoherent, and why Theodore Sider's Four-Dimensionalism (2001), the fullest defence of temporal parts, pairs them with eternalism as a matter of course. Yet consider the ancient Indian concept of kāla , which encompasses not just linear time but the cyclical nature of existence and the interconnectedness of all moments — the thought that each moment carries the others folded within it. The concept is not an analogue of the A-theory, and it decides nothing by itself; it serves here as a rhetorical precedent, a reminder that temporal elements can be conceived otherwise than as beads laid out on a tenseless string. The constructive work must be done by a distinction, to which I now turn: the distinction between the ontological status of temporal parts themselves and the ontological status of the moments they are usually taken to occupy. Constructing Temporal Parts in the Present The proposal is this. Retain the perdurantist's structural claim — the persisting object is an aggregate of temporal parts — but reject the eternalist's location claim, that these parts exist tenselessly at their several times. Instead, view the non-present temporal parts as constructions actualised within the dynamically unfolding present : structural components of the present object, individuated by historical causal relations and by potential