Jacobs, Caspar (2025) Against Presentist Velocities: Response to Gijsbers, 'Presentist Velocities'. BJPS Letters to the Editors.
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Abstract
Gijsbers has recently proposed an original theory of ‘presentist velocities’: the instantaneous relative positions and relative velocities of all bodies at the present instant are metaphysically fundamental, and their positions and velocities at both past and future times metaphysically depend on them. If physics is deterministic, then present such facts fully determine future such facts; if physics is indeterministic, then some past and future facts are indeterminate. The theory of presentist velocities solves some pernicious problems faced by other theories of velocity, such as the at-at theory. But Gijsbers’s presentation only considers classical mechanics, and does so in a relatively non-technical manner. If the theory of presentist velocities is to succeed, it should also work for more realistic physical theories. The aim of this letter is to show that the theory of presentist velocities falls short in this respect: once we look at the details of classical, statistical, and relativistic mechanics, presentist velocities face serious obstacles.
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| Item Type: | Published Article or Volume | ||||||
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| Keywords: | presentism; velocity; past hypothesis; invariance | ||||||
| Subjects: | Specific Sciences > Physics > Classical Physics Specific Sciences > Physics > Relativity Theory Specific Sciences > Physics > Statistical Mechanics/Thermodynamics Specific Sciences > Physics > Symmetries/Invariances |
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| Depositing User: | Caspar Jacobs | ||||||
| Date Deposited: | 15 Sep 2025 10:59 | ||||||
| Last Modified: | 15 Sep 2025 10:59 | ||||||
| Item ID: | 26656 | ||||||
| Journal or Publication Title: | BJPS Letters to the Editors | ||||||
| Official URL: | https://www.thebsps.org/letters/gijsbers-presentis... | ||||||
| Subjects: | Specific Sciences > Physics > Classical Physics Specific Sciences > Physics > Relativity Theory Specific Sciences > Physics > Statistical Mechanics/Thermodynamics Specific Sciences > Physics > Symmetries/Invariances |
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| Date: | 4 September 2025 | ||||||
| URI: | https://philsci-archive.pitt.edu/id/eprint/26656 |
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