1 Forthcoming in Foundations of Physics, 2000, 30, pp. 1605-1628. SUBSTANTIVALISM, RELATIONISM, AND STRUCTURAL SPACETIME REALISM 1 Mauro Dorato Department of Philosophy University of Rome 3 Via Ostiense 234, 00146 Rome, Italy e-mail dorato@uniroma3.it 1. Manifold substantivalism or metric field substantivalism? A historian of 20 th century philosophy of science that were to consider the recent renaissance of studies on the ontological status of spacetime would certainly notice a significant shift of interest toward metaphysical issues previously scorned by neopositivists philosophers. 2 Some philosophers more inclined toward historical analysis have complained about the audacious tendency of some contemporary philosophers of space and time to portray Newton and Leibniz (see Alexander 1956) as defenders of views that, like substantivalism and relationism, do not always represent in an accurate way the positions really taken by these historical figures (see Stein 1967 and DiSalle 1994). However, worse than such moderate forms of “interpretive violence” perpetrated on 17 th century natural philosophers – which in any case are not motivated by unfair attempts to add signifi- cance to one’s pet philosophical problem by ennobling its historical pedigree – is the fact that the current participants to the debate don’t even seem to agree about how to formulate “spacetime substantivalism” 3 within the fundamental spacetime theory of contemporary physics, the general theory of relativity. For example, it is not clear whether one should identify spacetime with the bare manifold or with the metric field. As is often the case when there is no agreement even about the nature of the problem, there is a natural tendency to affirm that 1 I want to thank Robert Rynasiewicz and Robert DiSalle for having read a previous version of this paper and having helped to remove some of my misinterpretations of their views. I am the only responsible for the remaining mistakes. 2 Such foundational studies were revived in the late eighties by the so-called “hole argument” due to John Earman and John Norton (1987). See Earman (1989), Butterfield (1989), Maudlin (1990), Rynasiewicz (1994), Healey (1995), DiSalle (1995) for discussions of the philosophical and metaphysical issues. The tendency to misrepresent Leibniz and Newton as defenders of relationism and substantivalism respectively was decisively more present in the philosophy of space and time of the first part of the century, and especially in Reichenbach. 3 Substantivalism is usually presented as the doctrine that space and time (spacetime) exist “over and above” the objects and events of the physical world, while relationism is regarded as a denial of just this thesis: a relationist about spacetime regards physical events and objects as the primary constituents of the world, and space and time as relations instantiated by such entities.