Conventionality and Reality in Special Relativity

Metaphysics of Science Seminar

3rd SESSION : CONVENTIONALITY AND REALITY IN SPECIAL RELATIVITY

Pieter Thyssen (UC LOUVAIN)

The debates on the conventionality of simultaneity and the dimensionality of the world have been central to the philosophy of special relativity. The former debate was sparked by Einstein in 1905 who took the notion of simultaneity to be conventional, rather than factual. The latter debate was initiated by Minkowski in 1908 who considered reality to be four-dimensional, rather than three-dimensional.

Both debates have lingered on to this day, without definite answers. Most strikingly, the link between both debates has remained largely underexplored. The purpose of this talk is to gauge what implications the former debate has for the latter. 

I first introduce the conventionality thesis and present the (in)famous Rietdijk–Putnam argument for the four dimensionality of the world. I then raise the so-called conventionality objection. I finally distinguish two possible readings of the conventionality thesis — an ontic and an epistemic one — and highlight the repercussions of this distinction for the conventionality objection.

I thus show the situation to be much more subtle than was previously argued and conclude somewhat undramatically that special relativity leaves the debate on the dimensionality of the world underdetermined.