In General Relativity (GR), it has been claimed that inertia receives a dynamical explanation. This is in contrast to the situation in other theories, such as Special Relativity, because the geodesic principle of GR can be derived from Einstein’s field equations. The claim can be challenged in different ways, all of which question whether the status of inertia in GR is physically different from its status in previous spacetime theories. In this paper I state the original argument for the claim (...) precisely, discuss the different objections to it and then propose a formulation that avoids the problems the original claim encounters. My conclusion is that one can say meaningfully that inertia is dynamically explained in GR. There are two senses in which the derivation of geodetic motion can be said to provide a (more) dynamical explanation of inertia in GR: it holds for any material test body that is a source of the gravitational field; and it is derivable without assuming inertial structures that are fixed independently of matter. (shrink)

The interpretation and justification of Earman’s symmetry principles (stating that any spacetime symmetry should be a dynamical symmetry and vice-versa) are controversial. This is directly connected to the question of how certain structures in physical theories acquire a spatiotemporal character. In this paper I address these issues from a perspective (arguably functionalist) that relates the classical discussion about the measurement and geometrical determination of space with a characterization of the notion of dynamical symmetry in which its application to subsystems that (...) act as measuring devices plays an essential role. I argue that in order to reformulate and justify Earman’s principles, and to provide a general account of the chronogeometrical character of some structures, the existence of a coordination between two notions of congruence, one mathematical and one dynamical, must be assumed for the interpretation of physical theories. This coordination provides the basis on which we can understand space-time in physical theories as the codification (representation) of certain features of the access ideal observers have to experience. (shrink)

Much discussion was inspired by the publication of Harvey Brown's book \textit{Physical Relativity} and the so-called dynamical approach to Special Relativity there advocated. At the center of the debate there is the question about the nature of the relation between spacetime and laws or, more specifically, between spacetime symmetries and the symmetries of laws. Originally, the relation was mainly assumed to be explanatory and the dispute expressed in terms of the arrow of explanation – whether it goes from spacetime (symmetries) (...) to (symmetries of) laws or vice-versa. Not everybody agreed with a setting that involves leaving ontology out. In a recent turn, the relation has been claimed to be analytical or definitional. In this paper I intend to examine critically this claim and propose a way to generally understand the relation between spacetime symmetries and symmetries of laws as deriving from constitutive principles. (shrink)

Dark matter is an essential ingredient of the present Standard Cosmological Model, according to which only 5% of the mass/energy content of our universe is made of ordinary matter. In recent times, it has been argued that certain cases of gravitational lensing represent a new type of evidence for the existence of DM. In a recent paper, Peter Kosso attempts to substantiate that claim. His argument is that, although in such cases DM is only detected by its gravitational effects, gravitational (...) lensing is a direct consequence of Einstein's Equivalence Principle and therefore the complete gravitational theory is not needed in order to derive such lensing effects. In this paper I critically examine Kosso's argument: I confront the notion of empirical evidence involved in the discussion and argue that EEP does not have enough power by itself to sustain the claim that gravitational lensing in the Bullet Cluster constitutes evidence for the DM Hypothesis. As a consequence of this, it is necessary to examine the details of alternative theories of gravity to decide whether certain empirical situations are indeed evidence for the existence of DM. It may well be correct that gravitational lensing does constitute evidence for the DM Hypothesis—at present it is controversial whether the proposed modifications of gravitation all need DM to account for the phenomenon of gravitational lensing and if so, of which kind—but this will not be a direct consequence of EEP. (shrink)

The question about the relation between spacetime structure and the symmetries of laws has received renewed attention in a recent discussion about the status of Minkowski spacetime in Special Relativity. In that context we find two extreme positions (either spacetime explains symmetries of laws or vice-versa) and a general assumption about the debate being mainly about explanation. The aim of this paper is twofold: first, to argue that the ontological dimension of the debate cannot be ignored; second, to claim that (...) taking ontology into account involves considering a third perspective on the relation between spacetime and symmetries of laws; one in which both terms would be somehow derived from common assumptions on the formulation of a given physical theory. (shrink)

It has been claimed, recently, that the fact that all the non-gravitational fields are locally Poincaré invariant and that these invariances coincide, in a certain regime, with the symmetries of the spacetime metric is miraculous in general relativity. In this paper I show that, in the context of GR, it is possible to account for these so-called miracles of relativity. The way to do so involves integrating the realisation that the gravitational field equations impose constraints on the behaviour of matter (...) in a novel interpretation of the equivalence principle, which dictates the determination of local inertial frames through gravitational interaction. This proposed explanation of the miracles can also deal with the problematic cases for attempts at explaining them in the context of the standard geometrical perspective on relativity theory. (shrink)

In this paper, I address the significance of the key notions of coordination, constitution and convention. My aim in so doing is to provide a better understanding of their relation to conventionalism and to evaluate the prospects for a version of the relativized a priori based on a refinement of the notion of coordination. I stress the Kantian roots of all three concepts. Moreover, I argue that the link between the early logical positivist requirement for the uniqueness of coordination and (...) the Kantian account of empirical objectivity provides an interpretive key that sheds light on the alleged incompatibility between constitutive principles and conventionalism. (shrink)

Kant afirma que espacio y tiempo son condiciones a priori de toda experiencia, a la vez que parece comprometerse con la naturaleza euclidiana del espacio y la simultaneidad absoluta. Su defensa del carácter a priori de estas nociones pasa por considerarlas intuiciones puras, de ahí que su naturaleza newtoniana parecería tener su origen en la configuración de lo que Kant llama intuición. No obstante, como muestran ciertas discusiones recientes, no está claro qué sea la intuición en Kant y cómo se (...) determina el espacio-tiempo a partir de ella. En este artículo, me acerco al debate sobre la procedencia de la síntesis de la intuición pura que, según Kant, determinaría la estructura espacio-temporal y discuto hasta que punto tener en cuenta la participación de las categorías en esta síntesis puede tener un efecto en el compromiso que, según la propuesta kantiana, uno debería asumir con respecto a una métrica determinada a priori. Mi conclusión es que el análisis kantiano da cabida, de forma natural, a que la determinación de la métrica espacio-temporal no esté dada a priori, en el sentido de universal y necesariamente. (shrink)

Kant states that space and time are a priori conditions of experience, while apparently being committed to the euclidean nature of space and absolute simultaneity. His defense of the a priori character of spatio-temporal notions stems from taking them as pure intuitions, so its newtonian nature would derive from the configuration of what Kant names as intuition. Nevertheless, according to some recent discussions, it is not clear what intuition means for Kant and how space-time is determined from it. In this (...) paper I look into the debate about the origin of the synthesis of pure intuition that, according to Kant, would determine the spatio-temporal structure. I discuss to what extent taking into account the participation of categories in such a synthesis might have an effect on the commitment that, according to the kantian perspective, one should have with respect to the metric being determined a priori. My conclusion is that kantian analysis can incorporate the idea of a spatio-temporal metric that is not given, in the sense of universally and necessarily, a priori. (shrink)