Tegmark offers the best explanation of the multitude of possible physical laws that exist in the Multiverse that I've come across and, in the process, downgrades fundamental physical laws to effective principles. This includes the mass of an electron. What still isn't clear to me is what a purely mathematical entity is composed of - 'composed of' is surely one of the many things Tegmark would immediately find wrong with my reading, but one I can't manage to get past. Somehow, the mathematical universe theory (MUH) solves for the problem of infinite regress that comes with the problem of what reality is 'composed of'. Properties of nature stem not from properties of its fundamental building blocks but from relations between those building blocks. What remains unclear is what those building blocks are. My intuition isn't a requirement for the truth of some external reality, but I'm unclear as to how you can describe relationships without an entity with which to relate.
Further reading:
Tegmark, 2007 (https://arxiv.org/pdf/0704.0646, The Mathematical Universe)