The Philosophy of Time: McTaggart, Presentism, Eternalism, and Bergson's Duration

Some questions philosophy inherits from every generation without ever returning them resolved. The question of time is, perhaps, the most stubborn of all. Augustine, in Confessions (Book XI), stated the paradox with a clarity that no subsequent philosopher has managed to surpass: “What, then, is time? If no one asks me, I know; if I wish to explain it to someone who asks, I do not know.” The difficulty is not rhetorical. Time is the condition of everything that exists — change, causality, memory, anticipation — and precisely because it is so pervasive, it escapes any attempt to define it from the outside, as though it were an object among others. This article traces the main knots in the contemporary metaphysics of time: McTaggart’s argument for the unreality of time, the debate between presentism and eternalism, the theory of temporal passage, Bergson’s durée, and the asymmetry between past and future.

1. McTaggart’s Argument: Is Time Unreal?

In 1908, the British philosopher J. M. E. McTaggart published in the journal Mind an article entitled “The Unreality of Time” — one of the most discussed texts in twentieth-century analytic metaphysics. McTaggart’s argument is structured around a distinction he himself introduced, one that has organized the entire debate ever since: the A-series and the B-series of time.

The B-series orders events according to the relation of earlier than and later than: Socrates’ birth precedes the death of Napoleon, which precedes the publication of McTaggart’s article, and so on. This series is permanent: if event X is earlier than event Y, that relation never changes. The B-series is therefore tenseless — it does not employ the predicates “past,” “present,” and “future.”

The A-series, by contrast, describes events as past, present, or future. These determinations are tensed and mutable: what is now future will become present and then past. It is in the A-series that we find what we intuitively call the flow of time — the sense that events approach, arrive, and recede.

McTaggart also postulated a C-series: the absolute order of events prior to any temporal determination, analogous to a spatial sequence. The B-series would be, in his system, the C-series furnished with a direction.

McTaggart’s central argument runs as follows: (1) genuine time requires change; (2) genuine change is only the change of A-series properties (an event passes from future to present, and from present to past); but (3) the A-series determinations are contradictory — every event is simultaneously past, present, and future, since all three properties apply to it at different times; (4) any attempt to resolve this contradiction by appealing to meta-properties of the A-series generates an infinite regress; therefore (5) the A-series is incoherent; therefore (6) time is unreal.

Most philosophers reject the conclusion, but the diagnosis remains influential: it forces a choice between two families of theory — A-theories (which take tensed determinations as fundamental) and B-theories (which reduce them to atemporal relations of earlier-than/later-than).

2. A-Theories and B-Theories: The Debate over Tense

A-theories (or tensed theories) hold that the present has a special ontological status — “now” is not merely a relative perspective, as “here” is in space, but an objective and privileged property of reality. The change of A-series properties is real. Presentism is the most radical form of A-theory.

B-theories (or tenseless theories) hold that temporal expressions like “now,” “yesterday,” and “soon” are indexicals — they function like “here,” “I,” or “this”: their referent shifts with the context of utterance, but there is no objective privileged property corresponding to an “absolute present.” D. H. Mellor, in Real Time (1981), developed the most influential version of B-theory with his token-reflexive account: a sentence like “the meeting is happening now” is true if and only if the meeting is simultaneous with the utterance of that sentence. No additional entity called “the present” is required. In Real Time II (1998), Mellor revised this position, replacing the token-reflexive analysis with a truthmaker-based approach — though both works remain central references for B-theory.

For the B-theorist, time is analogous to space: just as there is no “absolute here” in space, there is no “absolute now” in time. All moments exist equally — what gives us the sense of flow is merely the position we occupy in the temporal series, not a feature of time itself.

3. Ontological Positions: Presentism, Eternalism, and the Growing Block

The debate between A-theories and B-theories has an ontological counterpart: the question of which temporal entities exist.

Presentism holds that only the present exists. The past existed; the future will exist; but neither exists now. This position is closest to common sense — it seems obvious that dinosaurs no longer exist and that events of the twenty-third century do not yet exist. Presentism faces, however, serious difficulties with physics: in Einstein’s and Minkowski’s special theory of relativity, there is no absolute plane of simultaneity. The “present” of an observer depends on their state of motion — two events simultaneous for one observer may not be simultaneous for another. If the present is not absolute, the idea that “only the present exists” becomes problematic.

Eternalism (or the block universe theory) holds that past, present, and future exist equally, in the same way that different points in space exist equally. The universe is a four-dimensional “block” in which each event occupies a determinate position in three spatial dimensions and one temporal one. Minkowski’s spacetime geometry, fundamental to special relativity, naturally favors eternalism: in a four-dimensional spacetime, all events simply are — there is no ontological distinction between past and future, only relations of earlier-than. The “flow” of time would be an illusion produced by the observer’s perspective.

An intermediate position is the growing block universe, proposed by C. D. Broad in Scientific Thought (1923). According to Broad, the past and present exist — the past accumulates progressively — but the future does not yet exist. This position attempts to preserve the asymmetry between past and future without committing to strict presentism. It faces, however, the difficulty of explaining why the present should be ontologically privileged over the past.

4. The Problem of Temporal Passage and the Experience of “Now”

Even if we accept eternalism — the block universe — a question remains: why do we experience time as flowing? This is the question of temporal passage (or temporal becoming).

For the eternalist, passage is an illusion. What we call “now” is simply the moment at which we find ourselves in the temporal series — just as “here” is the place we occupy in space. But the analogy with space seems incomplete: we do not experience space as “flowing” from north to south, while time genuinely seems to move from past to future. The experience of passage is so ubiquitous and irresistible that reducing it to a mere illusion requires additional psychological and neuroscientific explanation.

Heidegger, in Being and Time (1927), approached the problem differently: for him, temporality is not a property of the external world that a subject contemplates, but the most fundamental existential structure of Dasein (human being-there). The human being exists as a projection toward the future from a past it carries as its “thrownness” — temporality is constitutive of the human mode of being, not a cosmological question. This phenomenological perspective avoids the problem of eternalism, but does so at the cost of leaving open the question of the “objective” time of physics.

Whitehead, in Process and Reality (1929), proposed a process metaphysics in which temporality is constitutive of reality at its most fundamental level: reality is made up of “occasions of experience” that perish upon reaching their completion, generating genuine flux and novelty — what Whitehead called “the creative advance into novelty.” For Whitehead, time is neither an illusion nor a purely formal structure, but the very mode by which reality produces itself. This process ontology stands in sharp contrast to substance ontologies, in which the fundamental entities are relatively stable persisting things that have temporal properties but are not reducible to them.

5. Bergson: Durée Against Spatialized Time

No philosopher attacked the reduction of time to space more forcefully than Henri Bergson. In his first book, Time and Free Will (published in French as Essai sur les données immédiates de la conscience, 1889), Bergson drew a radical distinction between the time of physics — a sequence of discrete, homogeneous instants, analogous to points on a line — and the time of consciousness, which he called durée (duration).

Durée is qualitative, heterogeneous, and continuous. It cannot be divided into instants without being destroyed, just as a musical melody cannot be reduced to the sum of isolated notes: what makes a melody this melody is precisely the way in which each note retains the preceding ones and anticipates those to come, forming an inseparable whole. Consciousness is that melody — a flow in which the past does not disappear but prolongs itself in the present, carrying within it all its accumulated thickness.

The time of science, by contrast, is spatialized: the physicist measures durations by comparing them with regular movements (the pendulum, the atomic clock), thereby converting time into measurable extension. This procedure is legitimate for practical and scientific purposes, but according to Bergson it falsifies the nature of real time by substituting the qualitative flow with a series of punctual instants, external to one another — like beads on a string rather than notes in a melody.

In Matter and Memory (1896), Bergson deepened this analysis: the past has not “passed” in the sense of having disappeared; it survives in pure memory and contracts into the present. The present is always “almost past” — it is the extreme point of contraction of the entire lived past. Bergson’s distinction between habit-memory (the past that lives in the body as a disposition to act) and pure memory (images of the past as it was) anticipates themes that philosophy of mind and neuroscience would revisit decades later.

Bergson’s most famous debate on time took place in 1922, at the Société française de philosophie, during a session at which Einstein was present. Bergson argued that Einstein’s relativity described the time of physicists — a measurable time relative to reference frames — but left untouched the lived duration of consciousness. Einstein replied that there was no “philosopher’s time” distinct from “physicist’s time.” The exchange, documented in Bergson’s Duration and Simultaneity (Durée et simultanéité, 1922), remains a subject of historiographical and philosophical debate: to what extent were the two interlocutors even discussing the same thing?

Whatever the verdict, Bergson’s contribution is enduring: he showed that any theory of time claiming to be complete must account for both the formal structure of physical time and the irreducible experience of lived temporality. The two dimensions can be theoretically distinguished, but they cannot simply be identified without philosophical loss.

6. The Arrow of Time: Entropy, Causality, and Asymmetry

The experience of time is radically asymmetrical: we remember the past, not the future; causes precede effects; eggs break but do not spontaneously reconstitute themselves. This asymmetry is what we call the arrow of time.

The philosophical problem is that the fundamental equations of classical physics (Newtonian mechanics) and quantum mechanics are, for the most part, symmetric under time reversal: if a process is permitted by the laws of physics, the reverse process is also permitted. How, then, does temporal asymmetry arise?

The most influential answer appeals to the second law of thermodynamics: the entropy of an isolated system tends to increase over time. Entropy measures the degree of macroscopic disorder of a system; its tendency to increase reflects the fact that there are vastly more microscopic “disordered” states than “ordered” ones. The thermodynamic arrow of time points in the direction of increasing entropy — from the past (low entropy) toward the future (high entropy).

This explanation, however, raises a further question: why did the universe have such low entropy in the past? The physical answer appeals to the initial conditions of the Big Bang — a question that transcends thermodynamics and touches cosmology and, ultimately, metaphysics. Philosopher Huw Price, in Time’s Arrow and Archimedes’ Point (1996), argued that temporal asymmetry is not an objective feature of physical time, but results from a perspective bias: we, as observers embedded in the causal flow of the universe, cannot adopt a timeless “Archimedean point” from which the symmetry would become apparent.

Causality is intimately linked to the arrow of time: causes precede effects, not the other way around. But if time is symmetric in physical laws, causal precedence becomes difficult to ground. David Lewis, in “Causation” (1973) and “The Paradoxes of Time Travel” (1976), explored both counterfactual causation and the logical consequences of time travel — showing that while travel to the past does not entail strict logical contradiction (a time traveler can visit the past without altering what already happened, satisfying a condition of “local consistency”), it imposes deeply counterintuitive constraints on what agents can do. Temporal logic, developed by Arthur Prior in the 1950s and 1960s, provides the formal tools for reasoning about statements whose truth value varies with time — a field now essential to computer science and artificial intelligence.

7. Assessment: Time as the Limit of Thought

The journey through this article reveals that time is perhaps the concept most resistant to philosophical intuition. When we try to fix it, it slips away: if the past no longer exists and the future does not yet exist, the present shrinks to a durationless instant — and time itself seems to dissolve. If we assert that all moments exist equally in the four-dimensional block, the passage of time becomes illusion — and with it our most immediate experience of being.

McTaggart showed that any coherent theory of time must take a stand: either tensed determinations (past, present, future) are objective and fundamental, or they are reducible to atemporal relations of earlier-than. Bergson showed that this choice cannot ignore the lived experience of duration, on pain of producing a theory of time that recognizes no one’s time. Relativistic physics showed that the absolute “now” is a Newtonian illusion — but has not told us what to put in its place for the life of consciousness.

Time is the medium in which all philosophical questions are formulated — and, paradoxically, one of the questions that philosophy is least able to answer. That is not a failure: it is the sign that we are facing a genuine question, in the deepest sense that Augustine knew how to express.

Essential Readings

• McTaggart, J. M. E. “The Unreality of Time.” Mind, vol. 17, no. 68, 1908, pp. 457–474.
• Mellor, D. H. Real Time. Cambridge: Cambridge University Press, 1981.
• Mellor, D. H. Real Time II. London: Routledge, 1998.
• Broad, C. D. Scientific Thought. London: Kegan Paul, 1923.
• Bergson, Henri. Time and Free Will [1889]. Trans. F. L. Pogson. London: George Allen & Unwin, 1910.
• Bergson, Henri. Matter and Memory [1896]. Trans. N. M. Paul and W. S. Palmer. New York: Zone Books, 1991.
• Bergson, Henri. Duration and Simultaneity [1922]. Trans. Leon Jacobson. Indianapolis: Bobbs-Merrill, 1965.
• Lewis, David. “The Paradoxes of Time Travel.” American Philosophical Quarterly, vol. 13, no. 2, 1976, pp. 145–152.
• Price, Huw. Time’s Arrow and Archimedes’ Point. Oxford: Oxford University Press, 1996.
• Sider, Theodore. Four-Dimensionalism: An Ontology of Persistence and Time. Oxford: Oxford University Press, 2001.
• Prior, Arthur N. Time and Modality. Oxford: Oxford University Press, 1957.

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