- Analytic metaphysics is in resurgence; there is renewed and vigorous interest in topics such as time, causation1, persistence, parthood and possible worlds. We who share this interest often pay lip-service to the idea that metaphysics should be informed by modern science; some take this duty very seriously. But there is also a widespread suspicion that science cannot really contribute to metaphysics, and that scientific findings grossly underdetermine metaphysical claims. For some, this prompts the thought ‘so much the worse for metaphysics’; others mutter ‘so much the worse for science’.
- One widely-discussed example is the apparent conflict between the special theory of relativity (STR) and presentism, the view that only what is present exists. According to STR, when we ask whether or not two distant events occur simultaneously, different frames of reference will dictate different answers; moreover, STR does not privilege any particular reference frame as giving the real or the most fundamental answer. For many pairs of events, there is no absolute fact of the matter as to whether or not they occur simultaneously. Presentists claim that only what is present exists, which is to say only those events simultaneous with now exist. But according to STR, it seems, there is no absolute fact of the matter as to which events are simultaneous with now. Unless we can believe that there is no absolute fact of the matter as to what exists, it looks as if we shouldn’t identify what exists with what is simultaneous with now. Thus presentism is false.
- Presentists have responded to this ‘refutation’ in a number of ways, by pointing out that the absence of a privileged reference frame in STR does not entail that there is no such frame, or by claiming that there could be an equally good scientific theory which involved a privileged reference frame, and was thus hospitable to presentism. Opponents argue that this is just so much squirming, and that presentists should simply face up to the fact that their theory, though it might initially have seemed appealing, has been rendered untenable by scientific progress.
- What bearing does STR have on presentism? How, if at all, is science relevant to metaphysics? We could settle the second question by proclamation, simply defining metaphysics to be the subject that begins where science ends. But imposing such a boundary between science and metaphysics will not settle interesting questions like the first. If we leave open the question whether metaphysics and science are mutually exclusive, we may disagree about whether modern physics sheds light upon metaphysical questions about the reality of the past and future. But if we impose a boundary between the disciplines, we may still disagree about whether questions about the reality of the past and future lie on the science side of the line or the metaphysics side.
- Although I will make some assumptions about the nature of metaphysical enquiry (see section 2, in particular), I will not attempt to define metaphysics. Instead, when I refer to ‘metaphysics’ or ‘metaphysical issues’, I mean issues of the sort typically discussed by self-described metaphysicians, who work in philosophy departments and publish in philosophy journals; issues which are typically taught to philosophy students in courses titled ‘metaphysics’. So questions about the nature of time, causation2, properties, numbers, persistence, possible worlds and so on will all count as metaphysical questions. This characterisation is intended to leave open the question whether scientists also work on these metaphysical questions.
- The Possibility of Metaphysics
- Optimism and Pessimism
- The Positions Characterised
- Optimism: There are actual cases in which the involvement of a metaphysical claim in an empirically successful scientific theory provides some reason to think that the claim is true.
- Radical Pessimism: The involvement of a metaphysical claim in an empirically successful scientific theory can never provide any reason to think that the claim is true.
- Moderate Pessimism: There is a kind of involvement in theory which, were a metaphysical claim to achieve this involvement, would provide some reason to think the claim is true; but there are no cases of metaphysical claims being involved in theory in this way.
- Scientific Realism and Radical Pessimism
- Scientific Realism, Moderate Pessimism and Optimism
- Metaphysicians’ Duties
- Presentism and Special Relativity
- Conclusions: Can science guide metaphysics? The choice between Radical Pessimism on the one hand and either Moderate Pessimism or Optimism on the other is an epistemological issue, in large part parasitic upon debates and decisions about scientific realism. The choice between Moderate Pessimism and Optimism is to be taken on the basis of case-by-case examination of potential contributions of science to metaphysics. The work of scientific realists provides us with a methodology for examining such cases, and suggests rules for debate. Most crucially, defenders of traditional metaphysics challenged by science must do more than just construct an ad hoc account which renders their own beliefs empirically adequate. They must provide an independently-motivated alternative science, or else demonstrate the overwhelming philosophical merit of their view. We cannot simply dismiss the metaphysics of science as scientists’ prejudices unless we work to justify this dismissal; but such work is not always doomed to fail. Science can be a guide to metaphysics, but it is not an infallible guide.
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