Growing Block

Core Idea and Historical Origins

The Growing Block theory of time (often simply Growing Block) is a position in analytic metaphysics that aims to reconcile the reality of temporal passage with an expanding inventory of what exists. It belongs to the family of A-theories of time, which treat tensed facts—what is past, present, or future—as fundamental features of reality, as opposed to B-theories, which regard all times as equally real and deny objective temporal becoming.

According to Growing Block, the past and present are real, forming a four-dimensional “block” of spacetime, but the future does not yet exist. As time passes, new events and entities come into being at the moving present, and the block of reality literally grows by the accretion of these newly real events. This differs from:

• Presentism, which holds that only the present exists (the past and future are unreal), and
• Eternalism or the block universe, which holds that past, present, and future all equally exist in a static four-dimensional manifold.

The metaphor of a “growing block” is usually traced to C. D. Broad, particularly in Scientific Thought (1923), where he describes a universe that increases as events that were once merely possible become determinate and real. In the late 20th and early 21st centuries, philosophers such as Michael Tooley, Peter Forrest, and Dean Zimmerman developed and refined the view as a systematic alternative to both presentism and eternalism.

Metaphysical Commitments

Growing Block involves a number of interrelated metaphysical claims about time and existence:

1. Ontological Asymmetry of Time

   • Past and present: Both are ontologically on a par and fully real. Past events (e.g., the signing of a treaty) and present events (e.g., a current conversation) inhabit the same four-dimensional structure.
   • Future: Future events are not yet part of that structure and thus do not exist. They may be possible or probable, but they are not real objects or events.

2. Objective Becoming and the Moving Present
   Growing Block posits a dynamic present that marks the frontier between the real (past and present) and the unreal (future). As the present “moves,” more of what was future becomes real, and the block increases in temporal extent. This becoming is taken as an objective, irreducible feature of the world, not merely a subjective impression.

3. Tensed Facts and Truthmaking
   On many versions, truths about the past are grounded in already real past events, while truths about the future lack current truthmakers because the relevant events do not yet exist. This has implications for debates on future contingents and whether statements about the future are presently true, false, or neither.

4. Compatibility with Relativity
   Growing Block must address the apparent tension with special relativity, which denies a unique, global present. Several strategies have been proposed:

   • Postulating a hidden preferred foliation of spacetime (a privileged slicing into simultaneity surfaces) that underwrites an objective present, even if it is not empirically detectable.
   • Reformulating the view in a relativistic way by treating growth as relative to frames or regions, though this can dilute the traditional notion of a single, global “now.”

5. Persistence and Personal Identity
   Because the past remains real, Growing Block typically supports endurantist or perdurantist accounts of persistence. An individual’s earlier temporal stages continue to exist, and one’s biography is literally contained within the growing block.

Arguments For and Against

Arguments in Favor

1. Capturing the Intuitive Reality of the Past
   Proponents argue that Growing Block explains why we treat the past as substantively real rather than mere fiction. Historical events, physical traces, and causal relations are naturally modeled as involving entities that still exist in a completed segment of spacetime.

2. Preserving Temporal Passage Without Ex Nihilo Creation of Total Reality
   Compared with presentism, which can be seen as annihilating the past and creating the present ex nihilo, Growing Block allows that reality accumulates. Nothing is lost; what is real never ceases to exist, it is simply located at earlier times. This can appear to match our sense that the world has a genuine history.

3. Middle Ground Between Presentism and Eternalism
   Growing Block is often presented as a compromise view:

   • Against eternalism, it maintains that the future is open and not yet real.
   • Against presentism, it upholds the ontological robustness of the past.

   This intermediate ontology is attractive to those who want both real becoming and real history.

4. Handling of Future Contingents
   Because future events do not yet exist, some defenders argue that future-tensed propositions (e.g., “There will be a sea battle tomorrow”) may be indeterminate in truth-value now, avoiding fatalistic arguments that assume the future is already fixed.

Objections and Criticisms

1. The Epistemic Objection (“Now-Problem”)
   A prominent challenge asks: if the past and present are equally real, how do we know we are at the growing edge rather than located somewhere in the past within the block? Every time slice would regard itself as present, yet only one is truly the frontier. Critics contend that Growing Block struggles to explain our privileged epistemic access to the real present.

2. Global Present and Relativity
   Many physicists and philosophers point out that a global present conflicts with relativity, which makes simultaneity frame-dependent. Unless Growing Block posits an undetectable preferred frame, it risks inconsistency with well-confirmed physical theory; if it does posit such a frame, it may be seen as ad hoc.

3. Asymmetry and the Direction of Time
   While Growing Block builds in a metaphysical asymmetry between past and future, critics question whether this adds more than standard accounts of the thermodynamic or causal arrow. Some argue that the direction of time can already be explained without positing an expanding block of reality.

4. Truth of Future-Tensed Statements
   If future facts lack truthmakers, it becomes difficult to preserve the intuitive bivalence of many future-tensed claims (e.g., predictions in reliable scientific contexts). Opponents argue that Growing Block either must accept non-bivalent future truths or weaken its denial of the existence of future events.

5. Overpopulation of Reality
   Since the past never ceases to exist, reality becomes ever more populous as time goes on. Some find this ontologically extravagant, especially if combined with a rich ontology of objects and events. Defenders ordinarily respond that ontological parsimony is less compelling than capturing temporal phenomena accurately.

Contemporary Developments

Contemporary discussions of the Growing Block theory focus on refining its formulation and testing its coherence with both metaphysics and physics.

1. Variants of Growing Block
   Philosophers distinguish between robust and more deflationary versions:

   • Robust variants treat becoming as an irreducible metaphysical feature and maintain a sharp ontological boundary between the existent past/present and non-existent future.
   • Deflationary variants may interpret growth in quasi-structural or modal terms, downplaying any “thick” metaphysical picture.

2. Integration with Physics
   Some theorists attempt to integrate Growing Block with speculative physical theories that allow for a form of dynamical spacetime (e.g., certain quantum gravity approaches). Others argue that a neo-Lorentzian interpretation of relativity—postulating a privileged frame—could provide the required background for a global present.

3. Links to the Philosophy of Religion and Modality
   In philosophy of religion, Growing Block is sometimes explored in relation to divine foreknowledge and providence: if the future is unreal, what is the status of God’s knowledge of future contingents? In modal metaphysics, the theory connects with debates about branching time, where multiple possible futures emanate from a single growing history.

4. Phenomenology and Experience of Time
   Some defenders appeal to the phenomenology of temporal passage, arguing that Growing Block offers a metaphysical picture closer to ordinary temporal experience than the static block universe. Critics reply that experiential data underdetermines the choice between competing theories and can be explained by psychological mechanisms alone.

As of current debates, Growing Block remains a prominent, though contested, option in the metaphysics of time. It serves as a focal point for exploring tensions between intuitive notions of temporal passage, formal physical theories, and competing demands of ontological parsimony and explanatory power. Whether a coherent, fully relativistic, and epistemically satisfactory version can be sustained is an ongoing question in contemporary philosophy.