Tense, Indexicality, and Consequence

This chapter outlines the problem of framing a theory of the temporal indicators of natural language in all their complexity and, in particular, of understanding the interaction of linguistic and contextual elements. It describes how the phenomenon of sequence of tense shows that tense logic is too limited, since it excludes the cross-reference typical of bound variables; it suggests instead that the tenses express temporal relations between events conceived as in Davidson. The particular discussion leads to the general question of the form of truth conditions for sentences in an indexical language. The discussion advocates conditional truth conditions, in which an antecedent clause spells out the import of the indexical elements. It goes on to describe two notions of a model for a language with such truth conditions, the notions varying as to whether the satisfaction of such antecedents is incorporated, and thus diverging in their conceptions of logical consequence.

On Relativity, Time Reckoning, and the Topology of Time Series

This chapter devotes equal attention to special relativity and general relativity. It first describes the history of the analysis of distant simultaneity, up to and including Einstein's procedure in his revolutionary 1905 paper which introduced special relativity. In particular, the discussion relates Einstein's procedure to the ensuing philosophical debate about whether distant simultaneity is a matter of convention. As to general relativity, the discussion gives a brief sketch of Einstein's path towards his discovery of general relativity. Thereafter, it focuses on the topological structure of time or, more precisely, of timelike lines (worldlines) in spacetime. It discusses the closed timelike lines first found in an exact solution of general relativity by Godel; and the open timelike geodesics that get arbitrarily close to the initial singularity (Big Bang) in a Friedmann solution.

The Perception of Time

This chapter aims to present a psychological model of how people perceive time, and to explain some experimental evidence supporting it. It suggests that the apparently close correspondence between the spatiotemporal structures of the perceived world and of the physical world, in contrast to the complex and controversial relation between, for example, perceived colour and light, lies at the root of the primary quality/secondary quality distinction. It also examines the neural mechanisms by which people keep track of time. The answer to this question is a model in which the nervous system itself produces temporal information, in the form of a ‘pacemaker’ or pacemakers that emit pulses at regular characteristic intervals; the model also includes a ‘calibration unit’ to allow for flexibility in the accuracy of timing. The chapter ends by surveying the experimental evidence for this model, including EEG studies.

Can There be a Literary Philosophy of Time?

This chapter takes the discussion of the metaphysics of time in a different direction. It asks whether the treatment of time in fictional narratives can teach anything about the nature of time, or the concepts and experience of it. In particular, it asks whether it can teach lessons that people cannot get from the usual philosophical studies of time. To pursue this question, the discussion assesses two main lines of thought that suggest the answer ‘Yes’. First, it focuses on such claims as that one can learn about time, and even about the self. Second, it considers the idea of appealing to a narrative with an unusual temporal structure, and to the ability to engage imaginatively with the narrative's time, to produce an argument that more usual structures are not necessary to time.

The Development of Machian Themes in the Twentieth Century

This chapter charts the complicated legacy of Mach's critique of absolute space and time. In 1902, Poincaré achieved a clear formulation of what a truly Machian mechanics should accomplish: it should permit a unique prediction of future motion on the basis of just the relative separations of bodies, and these separations' rates of change. However, this work made no impact on Einstein, despite his admiration for Mach. The discussion explains how several independent ideas that dominated Einstein's thinking about space, time and matter led him to a quite different interpretation (or misinterpretation) of Mach. This chapter also argues that, despite the misinterpretation, general relativity is perfectly Machian (in a sense that is the analogue for field theories of Poincaré's criterion), and that this shows general relativity to be ‘timeless’ in a certain sense, which is suggestive of quantum gravity.

The Problem of Time In Quantum Geometrodynamics

This chapter describes the problem of time in quantum geometrodynamics in more detail. It first describes how the fundamental equation of general relativity can be written as an instantaneous law, indeed as a cousin of a beautiful geometric theorem of Gauss, which Gauss called ‘theoremaegregium’. Then, it describes how the quantization of general relativity leads to the disappearance of time from the formalism, and surveys three ways to respond to the problem. First, one can try to extract a notion of time that will not ‘disappear’ under quantization, from the formalism of classical general relativity. Second, one can try to find a time in the formalism of quantized general relativity. Third, one can conclude that time is only an approximate notion: quantum geometrodynamics, and perhaps quantum theory generally, are to be interpreted in a fundamentally timeless way.

The Metaphysics of Time

This chapter maintains that the two broad positions in the temporal becoming debate are too broad; that is, each is a conjunction of metaphysical theses, and these are in general logically independent of each other. Furthermore, it notes that the truth ‘lies in the middle’. It argues for a temporal becoming in the sense that what facts are actual varies with time. And arguments relating to counterfactuals and to causation suggest that facts never cease to exist, so that actuality ‘grows’ by accretion of facts. On the other hand, the opponents of temporal becoming are right in some of their claims, such as that tensed properties are relational, not intrinsic, and that tensed concepts are not basic in conceptual analysis. The discussion favours analysing temporal priority as a causal relation between spacetime points.

A Century of Time

This chapter argues for the position of temporal becoming across a wide variety of fields. The chapter's central sections address successively the metaphysics, physics and logic of time. It rebuts McTaggart's argument that temporal becoming involves a contradiction. It admits that special relativity's frame — dependence of simultaneity is inimical to temporal becoming. However it also argues that temporal becoming is rehabilitated both by general relativity's allowance of cosmic time functions and, more fundamentally, by the collapse of the wave-packet in quantum theory. Finally, the discussion considers the logic of time, especially tense logic, and applies this to recent cosmological speculation about the Big Bang and more generally to the idea of the beginning of time.

On the Emergence of Time in Quantum Gravity

This chapter discusses the idea that the treatment of time in present-day physical theories, general relativity and quantum theory, might be an approximation to a very different treatment in the as yet unknown quantum theory of gravity. It considers the general idea that one theory could be emergent from another, emergence being a relation analogous to, but weaker than, intertheoretic reduction. It also gives a broad description of the search for a quantum theory of gravity and some of its interpretative problems. Thereafter, the discussion focuses on the emergence of time in two specific quantum gravity programmes: quantum geometrodynamics and the Euclidean programme. It also addresses the so-called ‘problem of time’. It is really a cluster of problems; technical and conceptual, arising from how time is treated very differently in general relativity and quantum theory.