Presentism, Eternalism, and the Growing Block

The A-theory/B-theory distinction concerns whether tense is real. Cutting across it is a distinct question about ontology: which times, and which objects, exist? Do only present things exist, or are past and future things equally real? This is the dispute among presentism, eternalism, the growing block, and the moving spotlight — the four main positions on the existence of times. It is easy to conflate with the A/B debate but genuinely separate: the A/B question is about the status of tensed facts, this one about the extent of the temporal world.

This page sets out the four views, their motivations, and the objections that press each; the underlying tense debate is on the A-theory/B-theory page, and the physical challenge on the relativity of simultaneity and block universe pages.

The four positions

The views differ over what is included in the domain of existence — read "exists" tenselessly, as the widest "there is."

• Presentism. Only what exists now exists at all. Dinosaurs do not exist (they did); Mars colonies do not exist (they will, perhaps). Reality is a single momentary slice, continually replaced. This is the most natural, "common-sense" view and the paradigm A-theory: the present is not just privileged but exhaustive.
• Eternalism. All times are equally real; past, present, and future events all exist tenselessly, differing only in their temporal location, just as distant places exist though they are not here. Reality is a four-dimensional block, and "now" picks out one's own temporal position, nothing metaphysically special. This is the natural home of the B-theory and of four-dimensional persistence.
• Growing block (C. D. Broad). The past and present are real and the future is not; reality is a block that grows as time passes, accreting new slices at the objective present, which is its leading edge. It combines the eternalist's real past with the A-theorist's open future and objective becoming.
• Moving spotlight. All times exist (as in eternalism), but one of them is, in addition, objectively and monadically present — as if a spotlight of presentness moves along the fixed block, illuminating each moment in turn. It grafts a real, moving A-series present onto a permanent B-series block.

The case for each — and the objections

Presentism

For: It respects common sense and the manifest reality of change; it takes the experience of passage at face value; it keeps the future genuinely open, which suits libertarian free will. It has an elegant, minimal ontology — one slice.

Against:

• The truthmaker problem. "There were dinosaurs" is true. What makes it true, if the past does not exist? There are no dinosaurs, and (for the presentist) no past facts, to serve as truthmakers. Presentists respond with present-tense surrogates — presently existing properties of the world ("Lucretian" past-tense properties), "ersatz" abstract times, or a primitive tensed operator — each of which critics find ad hoc or ontologically cheating.
• Cross-temporal relations. Abraham Lincoln is admired by people now; a cause is earlier than its effect. Such relations seem to need both relata to exist. If Lincoln does not exist, what is the relation to?
• The relativity objection (decisive, for many). Presentism needs a global, frame-independent present — a worldwide "now." But special relativity denies exactly this: simultaneity is frame-relative, so there is no observer-independent set of events that are "present." The Rietdijk–Putnam argument turns this into a case against presentism and for eternalism. Presentists must either relativise existence to frames, shrink the present to a single point (point-presentism), or adopt a controversial neo-Lorentzian preferred foliation.

Eternalism

For: It fits relativity effortlessly — no privileged present is needed, and the block universe is its natural picture. It solves the truthmaker and cross-temporal-relation problems trivially, since past and future relata exist. It meshes with four-dimensionalism about objects.

Against:

• The loss of passage. If all times are equally real and nothing is objectively present, then time does not flow and our sense that it does is an illusion — which many find incredible (the "moving now" seems undeniable). The eternalist must supply a deflationary account of temporal experience.
• The "why now?" and the openness of the future. Eternalism seems to make the future as fixed as the past, straining the sense that the future is open and our deliberation efficacious (a worry connected to fatalism, though eternalists deny it entails fatalism).

Growing block

For: A principled compromise — a real, determinate past (good for truthmakers) plus an open future and genuine becoming (good for the A-theory).

Against: The "how do you know you're present?" (dead past) objection: if past moments are just as real as the present one, and each was the growing edge, why think this moment is the current edge rather than some long-dead slice that is equally real and equally "feels" present? The view seems to undercut our confidence that we are at the leading edge. It also inherits the relativity problem, since the growing edge is a global present.

Moving spotlight

For: Keeps the eternalist's tidy block and an objective, moving present, honouring both physics-friendly ontology and the reality of passage.

Against: It looks like the worst of both worlds to critics: it posits a moving present whose motion faces the rate-of-passage regress, yet the underlying block already contains everything, so the "spotlight" seems to do no work — an idle metaphysical extra. Like the others in its family, it needs a global present that relativity resists.

The two questions kept apart

It bears repeating that the A/B question and the presentism/eternalism question are distinct axes:

• Presentism, growing block, and moving spotlight are all A-theories (they posit an objective present) but differ sharply in ontology (one slice / a growing block / a full block with a spotlight).
• Eternalism is the standard B-theory ontology, but one can in principle be an eternalist who still thinks tense is primitive — the positions are not perfectly locked together, which is why the debates are run separately.

Where this sits

The presentism/eternalism dispute is the ontological face of the temporal question, layered on top of the tense debate and inheriting McTaggart's framing. Its outcome is powerfully shaped by physics: the relativity of simultaneity and the block universe tilt the field toward eternalism, while the intuition of passage and the openness of the future pull back toward presentism. Which times exist also settles how objects persist through them — the subject of the endurantism/perdurantism page. The next page confronts the phenomenon all four views must reckon with: the apparent passage of time.