I've been thinking about something to recommend, since it's a bit ridiculous to end a relativistic exposition without settling the uncertainty into some new, interesting starting point.

Minimum description length might be just the right place.

[0] https://en.wikipedia.org/wiki/Minimum_description_length

[1] https://www.amazon.com/Description-Principle-Adaptive-Comput...

Alternately, generating functions.

[2] https://en.wikipedia.org/wiki/Generating_function

[3] https://www.amazon.com/generatingfunctionology-Third-Herbert...

Alternately alternately, various categorical notions.

[4] https://en.wikipedia.org/wiki/Realizability

[5] http://stijnvermeeren.be/download/mathematics/essay.pdf

[6] https://ncatlab.org/nlab/show/locally+presentable+categories...

[7] https://ncatlab.org/nlab/show/groupoid+cardinality

Alternately alternately alternately, foundational madness of the best kind.

[8] http://www.forkinganddividing.com/

[9] https://www.amazon.com/Blind-Spot-Lectures-Logic/dp/30371908...