Patrick Dawson

ABSTRACT Doomsday is the last moment in time. Nothing comes after. In the recent literature on temporal metaphysics, several theories have recently been challenged by arguments invoking doomsday. A shared premise in these arguments is that it would be a problem or drawback for a theory of time, if it failed to allow for moments of undetermined doomsday. In such moments, time ends without being determined to do so by the laws plus the state of the world at that moment. In this paper, I argue against this premise. In general, if a theory of time is incompatible with undetermined doomsday, that is just an interesting but neutral consequence of that theory. My argument also serves to illustrate a broader point: namely, that because doomsday is a complex and alien scenario, it is difficult to raise arguments against any particular theory of time premised on assumptions about how doomsday might occur.

Presentists deny that past or future things exist. Some presentists also deny that there are any underlying truths about the past or future. While this seems to conflict with our everyday tensed discourse, presentists might avoid conflict by adopting a theory of hermeneutic fictionalism about the non-present. Under such a theory, everyday utterances of non-present-tensed sentences are taken to engage with a fiction, rather than expressing truths about the past or future. In this paper I defend a specific version of this view: meta-fictionalism about the non-present. Under this view there is a socially-understood non-present fiction, a 'story of history', derived from apparent records existing in the present. Meta-fictionalists take our everyday tensed discourse to involve assertions about the content of that fiction. I argue that this view is plausible, and that it fares better than pretence fictionalism, a competing view that has already seen discussion in the literature.

The aim of this thesis is to defend a presentist metaphysics. I respond to a series of objections against presentism, including some that draw on our best physics. I also explore ways in which presentism might play an active role in interpreting and constraining physical theory, beyond merely being consistent with it. A unifying theme of this thesis is that I advocate for a reduction of presentism to its bare essentials. Within the proposed ontology, reality is three-dimensional. Time only exists in the sense that three-dimensional reality primitively changes. I reject any temporal dimension, extension, or direction. I reject any primitively tensed facts or nonpresent-tensed truths. I also reject any notion of simultaneity, beyond the mere fact that multiple entities exist in the three-dimensional world. I accept and embrace that if ontology is ‘stripped back’ to the present, then other features of metaphysics that depend on ontology should be stripped back too. The world, under this view, is a forgetful one. What we call the ‘past’ has been utterly lost from existence: there are not even any absolute facts or truths about how things once were. All that remain are records, memories, and the like, but there are no objective underlying truths to which those records correspond. This has implications for physics. In a forgetful world particles have positions, but no entire trajectories. The present may be certain and determinate, but the past and future are at best modelled using probabilistic mathematics. I believe that the world is likely to be as I describe. I will not attempt to argue, however, that this view is intuitive. Instead I will argue that it can account for our experiences and observations, including those from physics, in a simple and effective way. Most importantly, I argue that this view succeeds in the face of challenges where other versions of presentism fail.

Presentists believe that only present things exist. Their theories, at first glance, seem to offer many admirable features: a simple ontology, and a meaningful, objective status for key temporal phenomena, such as the present moment and the passage of time. So intuitive is this theory that, as John Bigelow puts it, presentism was “believed by everyone...until at least the nineteenth century”. Yet, in the last 200 years presentism has been beset by criticisms from both physicists and metaphysicians. One of the most significant criticisms is that presentists cannot provide an acceptable system of truthmaking. If there is no past, how can there still be truths about the past? In this paper, I introduce a new theory of presentism, which addresses this problem in a novel way: by simply denying that there are any truths about the past. While prima facie an unintuitive position, I will argue that a sensible presentist philosophy of this kind can be described, so long as it is accompanied by an appropriate system of physics. I will also indicate at certain points that adopting presentism could allow us to understand fundamental physics in new, more intuitive ways. By the end of the paper, I hope to not only show that hard presentism is a defensible theory of time, but also that it could offer a number of advantages to the physicist and the philosopher alike.