Convention and Fact: Poincaré’s Conventionalism and the Corpus’s “Scaffolding” (the Defined Value of c, Unit Conventions).
The corpus has repeatedly separated “the description we choose (the Layer-2 lens)” from “the fact nature forces (Layer 1).” The philosopher who first drew this line sharply was Henri Poincaré, with his CONVENTIONALISM. In Science and Hypothesis (1902) he argued that the geometry of space (Euclidean/non-Euclidean) is not forced by nature but a convention chosen for convenience — “one geometry cannot be more true than another; it can only be more convenient.” Geometry is tested only together with the physical laws (rods, light rays, force laws), so changing the geometry and adjusting the physics reproduces the same observations. This paper applies that discipline to the corpus’s “scaffolding”: the corpus’s “c is scaffolding (a defined value)” (Paper 66) means the NUMERICAL VALUE of c is a convention — c has been an exactly defined constant since the 1983 definition of the metre, and the 2019 SI revision fixed h, e, k_B, N_A as defining constants. By contrast, that c is FINITE (an invariant speed exists, Paper 83), that gravity (curvature) exists, and that space is nearly 3-dimensional (Paper 69) are not conventions but facts forced by experiment. Conventionalism is NOT “anything goes”: experiment constrains the whole geometry+physics package, and — honestly — general relativity made spacetime geometry dynamical and empirical, LIMITING strict conventionalism. The correct position: the package is constrained by experience, with a conventional split (which part is geometry, which is physics; coordinative definitions) remaining inside. IMPORTANT (scope): a Layer-2 structural interpretation of philosophy of science; no new mathematics and no new prediction. The Universe OS is a Layer-3 non-science lens.
On the making of this work: The ideas and content of this work stem from the author’s own considerations. Assistance from an AI (a large language model) was used for structuring, English translation, and checking the algebra. Any remaining errors or misinterpretations are solely the author’s. Feedback and corrections are sincerely appreciated.
Reference
Yamagishi, Y. (2026). Convention and Fact [Paper 95]. Zenodo.
DOI: 10.5281/zenodo.21758621
ORCID: 0009-0006-8587-3450