The British Journal for the Philosophy of Science Advance Access originally published online on November 14, 2005
The British Journal for the Philosophy of Science 2006 57(1):1-45; doi:10.1093/bjps/axi150
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The Rotating Discs Argument Defeated
All Souls College, Oxford OX1 4AL, England jb56{at}cus.cam.ac.uk; jeremy.butterfield{at}all-souls.oxford.ac.uk
The rotating discs argument (RDA) against perdurantism has been mostly discussed by metaphysicians, though the argument of course appeals to ideas from classical mechanics, especially about rotation. In contrast, I assess the RDA from the perspective of the philosophy of physics. I argue for three main conclusions. The first conclusion is that the RDA can be formulated more strongly than is usually recognized: it is not necessary to imagine away the dynamical effects of rotation. The second is that in general relativity, the RDA fails because of frame-dragging. The third conclusion is that even setting aside general relativity, the strong formulation of the RDA can after all be defeated, namely, by the perdurantist taking objects in classical mechanics (whether point-particles or continuous bodies) to have only temporally extended (i.e. non-instantaneous) temporal parts, which immediately blocks the RDA. Admittedly, this version of perdurantism defines persistence in a weaker sense of definition than pointilliste versions that aim to define persistence assuming only instantaneous temporal parts. But I argue that temporally extended temporal parts (i) can do the jobs within the endurantismperdurantism debate that the perdurantist wants temporal parts to do and (ii) are supported by both classical and quantum mechanics.
- Introduction
- The story so far
- 2.1 The RDA
- 2.2 Intrinsic properties and the idea of velocity
- 2.2.1 The intrinsicextrinsic distinction
- 2.2.2 Velocity to the rescue?
- 2.2.2 Velocity to the rescue?
- 2.3 Naturalism
- 2.4 The accompaniments of rotation
- 2.5 Two kinds of reply: against the consensus
- 2.2 Intrinsic properties and the idea of velocity
- 2.1 The RDA
- Describing rotation
- 3.1 Rotation is kinematic
- 3.2 Beware of rigidity
- 3.3 An improved RDA: allowing the actual accompaniments
- 3.4 The RDA fails in general relativity
- 3.2 Beware of rigidity
- 3.1 Rotation is kinematic
- Perdurantism without tears: the classical case
- 4.1 Rejecting instantaneous temporal parts
- 4.2 Replying to the RDA
- 4.2.1 Kinematics
- 4.2.2 Dynamics
- 4.2.3 An anti-pointilliste objection and reply
- 4.2.2 Dynamics
- 4.3 Intrinsic properties of non-instantaneous temporal parts
- 4.3.1 Can the perdurantist appeal to them?
- 4.3.2 Temporal intrinsicality at an instant is rare
- 4.3.3 A better reason for temporal intrinsicality
- 4.3.2 Temporal intrinsicality at an instant is rare
- 4.4 Non-instantaneous parts can do the jobs
- 4.4.1 Humean supervenience revisited
- 4.4.2 The problem of change
- 4.4.3 Puzzles of coincidence
- 4.4.2 The problem of change
- 4.5 Instantaneous velocity is hardly extrinsic
- 4.2 Replying to the RDA
- 4.1 Rejecting instantaneous temporal parts
- Support from decoherence in quantum theory
- 5.1 Classical and quantum: relativizing the intrinsicextrinsic distinction
- 5.1.1 Unitarity: momentum as temporally intrinsic
- 5.2 Position and existence as nomically extrinsic
- 5.1.1 Unitarity: momentum as temporally intrinsic
- 5.1 Classical and quantum: relativizing the intrinsicextrinsic distinction