Exterminous Hypertime

This paper investigates ‘exterminous hypertime’, a model of time travel in which time travellers can change the past in virtue of there being two dimensions of time. This paper has three parts. Part one discusses the laws which might govern the connection between different ‘hypertimes’, showing that there are no problems with overdetermination. Part two examines a set of laws that mean changes to history take a period of hypertime to propagate through to the present. Those laws are of interest because: (i) at such worlds, a particular problem for non-Ludovician time travel (‘the multiple time travellers’ problem) is avoided; and (ii) they allow us to make sense of certain fictional narratives. Part three discusses how to understand expectations and rational decision making in a world with two dimensions of time. I end with an appendix discussing how the different theories in the metaphysics of time (e.g., tensed/tenseless theories and presentism/eternalism/growing block theory) marry up with exterminous hypertime.

Reappraising Braid after a Quantum Theory of Time

Braid’s (Jonathan Blow, 2008) time-bending gameplay allows players to engage with a virtual world in which a player’s perceived ‘past’ can be endlessly rewritten, duration extended, and the ludic arrow of time can be reversed. One could assume that as mistakes can simply be undone, in-game actions cease to have consequences. However, the climax of the game’s narrative arc disrupts our assumption of control over these mechanics and encourages players to reflect on the possible moral implications of actions, both in context of the game world and—through careful invocation of real-world scientific experiments—on everyday life. In this paper, I propose that Braid uses gameplay to explore the difficulty of making moral judgements in a world without an objective past. This is, for the most part, achieved through Braid’s utilization of a specific interpretation of quantum theory—in accordance with the game’s lead designer, Jonathan Blow—that “starts to threaten our very existence” by questioning the possibility of a singular, objective, real ‘past’ and the possibility of a definitive account of past actions. I first argue that the game’s mechanics immerse players in a game world inspired by Blow’s understanding of quantum mechanics. Placing an emphasis on certain technical aspects, I outline how the functioning of the game’s central rewind mechanic—although initially seeming to reinforce visions of our reality consistent with C.D. Broad’s ‘growing block’ theory—questions the notion of an objective past and so resonates strongly with both the work of J.A. Wheeler and an agential realist theory of time. With this understanding in place, I go on to analyze the climax of the game, reading it as an exploration of—and challenge to—the role of a presumed objective ‘past’ in understanding the morality of a given situation. Finally, through a reading of the game’s closing moments, I suggest Braid promotes a turn to individual responsibility for agency; Braid, I argue, recommends one accept the continuing existence and changeability of the past within the present while embracing one’s own role in the shared process of constantly remaking reality and history. As a result, well-intentioned actions in the present are framed as more important than a focus on precedent to predict outcomes, making a cautious suggestion on how one might live without reference to an objective existence. Although I highlight some of the wider ramifications of this at the end of this paper, Braid is far from a fully developed ethical system; it stands, however, as an engaging attempt to formulate a comment on time, temporality and morality through interactive media.

Haecceity and thisness

A ‘haecceity’ (from the Latin, haecceitas, which translates literally as ‘thisness’) is a certain kind of property. In broad outline, a thisness is a primitive, particular, nonqualitative property of an individual, i.e. the property of being a specific individual (or, perhaps, the property of being identical with a specific individual). For example, Ruth Barcan Marcus’s thisness is the property being (identical with) Ruth Barcan Marcus, and so on for all individuals. To clarify: although it is typical to see a thisness described as the property of being identical with an individual, it is not merely the property of being self-identical, which all individuals exemplify trivially; it is a special kind of property that is uniquely exemplified by its bearer. And so, for any individual x, since the property being (identical with) x is both uniquely exemplified by x and essential to x, so x’s thisness is a nonqualitative individual essence of x. The terminology of ‘haecceity’ and ‘thisness’ derives from the work of John Duns Scotus (c.1266–1308) and some of Scotus’s insights and application of thisnesses are still relevant to debates about identity and individuation. This terminology has its roots in the scholastic philosophy of the High Middle Ages and it was revived in contemporary metaphysics by the work of Robert Merrihew Adams in the second half of the 20th century. In addition to the question of what is the metaphysical nature of a thisness, a considerable amount of the debate concerns what thisnesses can do to ‘earn their keep’ in a systematic metaphysics. Some say that accepting an ontology of thisness permits the individuation of qualitatively indiscernible objects or events – with appropriate footnotes to Scotus. Others say that accepting a specific ontology of thisness allows one to defend certain positions in the philosophy of time, i.e. the growing block theory of time, or presentism. We are concerned here with haecceities (thisnesses) and not ‘haecceitism’, the view that a world could not be nonqualitatively different without a qualitative difference.

Metaphysics of laws and ontology of time

At first glance, every metaphysics of laws (Humeanism, primitivism, Power metaphysics) can be combined with every ontology of time (eternalism, growing block, presentism). In contrast, the paper intends to show that Humeanism requires eternalism and that Power metaphysics must presuppose an existentially dynamical view of temporal existence, i.e. growing block or presentism. The presented arguments turn out to be completely independent of whether the laws of nature are deterministic or probabilistic: the world is non-productive and static or productively dynamical, the future be ‘open’ or not.

Temporal Paradoxes

Chapter 2 surveys the various theories of time and explores their consequences for the possibility of time travel. Section 1 introduces the traditional debates over tense and distinguishes between three different views of temporal ontology: eternalism, presentism, and the growing block theory. Section 2 discusses eternalism and the double-occupancy paradox. Section 3 focuses on presentism and various versions of the “no destination” objection. Section 4 looks at the growing block theory and the worry that time travel would allow for future indeterminacy to creep back into the past. Finally, sections 5 and 6 look at the special and general theories of relativity and consider their implications for our understanding of time travel.