Online research in philosophy

Extending on an earlier paper [Found. Phys. Ltt., 16(4) 343–355, (2003)], it is argued that instants of time and the instantaneous (including instantaneous relative position) do not actually exist. This conclusion, one which is also argued to represent the correct solution to Zeno’s motion paradoxes, has several implications for modern physics and for our philosophical view of time, including that time and space cannot be quantized; that contrary to common interpretation, motion and change are compatible with the “block” universe and relativity; and that time, space, and space-time too, cannot exist. Instead, motion and change become the major players.

In this note I raise a new problem for backwards time travel, and make some first suggestions as to how it might be solved. I call it the motivation problem. It is not a logical or a metaphysical problem, but a psychological one. It does not impact upon the possibility, or even the likelihood, of backwards time travel. Yet it is deeply puzzling, and we will have no idea what time travel would actually be like until we explore it. Thus, where other problems for backward time travel assume that we know what time travel would be like, and argue that we cannot have it, this new problem gives us no reason to think that we cannot have time travel, but argues that we have much less idea than we usually suppose about what it would really be like to travel back in time.

The aim of Jonathan Tallant’s recent article ‘What is B-time?’ (2007) is to demonstrate that B-time - which holds that time consists solely of tenseless temporal relations - is something of which we have no understanding, and that, therefore, if mind-independent time is B-time, then time is unreal. Of course, implicit in his own position is that since time is plausibly real and we do understand what time is, the correct ontology of time is A-time or tensed time. How then does Tallant purport to substantiate the crucial claim that ‘we have no understanding of what “B-time” is’ (2007: 147)? The overall structure of his argument may be stated as follows:1 Argument A..

In this course we will examine several philosophical puzzles concerning time. We all seem to experience time in a very fundamental and direct way. Yet once we begin to reflect on what time really is, it is easy to feel as puzzled as St Augustine was, who wrote: “If no one asks me, I know what [time] is. If I wish to explain it to him who asks me, I do not know.” The first set of issues we will discuss concern the question whether time is ‘real.’ Time appears to consist of past, present and future. But do the past and the future exist in the same way as the present or is only the present real? Does time ‘flow’? In what ways is time different from space? What would it be to ‘spatialize’ time? Next we will ask whether certain views of time imply that there can be no freedom of the will. One might worry that if facts about the future (including facts about what I will do tomorrow) already existed in the same way as facts about the present exist, then I could not be free to choose what I will do. After all, how can I be free to decide to skip class tomorrow, if it is ‘already’ a fact today that I will attend class? What, if anything, is the connection between various views of time and ‘fatalism’? The third topic we will discuss is time travel. First we will ask whether time travel is a conceptual possibility. As we will see, there are certain conceptual puzzles associated with the possibility of time travel. For example, one might think that if time travel is possible, then I should be able to travel back in time and kill my father before the date of my conception. But this scenario seems to lead to a contradiction. Some have taken considerations such as these to argue that the very idea of time travel is incoherent. Is this right? If not, why not? Then we will look at what the theory of relativity says about the nature of time in general and about the physical possibility of time travel more specifically. Finally we will examine several issues concerning the asymmetry of time..

By analyzing the meaning of time I argue, without endorsing operationalism, that time is necessarily related to physical systems which can serve as clocks. This leads to a version of relationism about time which entails that there is no time 'before' the universe. Three notions of metaphysical 'time' (associated, respectively, with time as a mathematical concept, substantivalism, and modal relationism) which might support the idea of time 'before' the universe are discussed. I argue that there are no good reasons to believe that metaphysical 'time' can be identified with what we ordinarily call time. I also briefly review and criticize the idea of time 'before' the big bang, associated with some recent speculative models in modern cosmology, and I argue that if the big bang model is a (roughly) correct description of our universe, then the best current answer to the question in the title is that time did have a beginning.

This paper presents a critical examination of claims advanced by several philosophers to the effect that 'time travel' represents a physical possibility and that the interpretation of certain actually observed phenomena in terms of 'time travel' is both legitimate and advantageous. It is argued that (a) no convincing motivation for the introduction of the time travel hypothesis has been presented; (b) no coherent and interesting sense of 'going backward in time' has been supplied which makes 'time travel' compatible with Special Relativity; (c) even the conceptual possibility of 'time travel' is an unsettled and somewhat nebulous question.

Thinking about time travel is an entertaining way to explore how to understand time and its location in the broad conceptual landscape that includes causation, fate, action, possibility, experience, and reality. It is uncontroversial that time travel towards the future exists, and time travel to the past is generally recognized as permitted by Einstein’s general theory of relativity, though no one knows yet whether nature truly allows it. Coherent time travel stories have added flair to traditional debates over the metaphysical status of the past, the reality of temporal passage, and the existence of free will. Moreover, plausible models of time travel and time machines can be used to investigate the subtle relation between space-time structure and causality.

It surveys some philosophical issues concerning time travel and should serves as a quick introduction. It includes a new and improved way to define a time machine.

In the present paper, I offer a new argument to show that presentism about time is incompatible with time travel. Time travel requires leaving the present, which, under presentism, contains all of reality. Therefore to leave the present moment is to leave reality entirely; i.e. to go out of existence. Presentist “time travel” is therefore best seen as a form of suicide, not as a mode of transportation. Eternalists about time do not face the same difficulty, and time travel is compossible with eternalism.

Discussions of the nature of time, and of various issues related to time, have always featured prominently in philosophy, but they have been especially important since the beginning of the 20th Century. This article contains a brief overview of some of the main topics in the philosophy of time — Fatalism; Reductionism and Platonism with respect to time; the topology of time; McTaggart's arguments; The A Theory and The B Theory; Presentism, Eternalism, and The Growing Universe Theory; time travel; and the 3D/4D controversy — together with some suggestions for further reading on each topic, and a bibliography.