>>369
>「従来の種の理論」って何だよ

良い質問だ
https://en.wikipedia.org/wiki/Combinatorial_species
Combinatorial species
Category theory provides a useful language for the concepts that arise here, but it is not necessary to understand categories before being able to work with species.
The category of species is equivalent to the category of symmetric sequences in finite sets.[1]

https://www.kurims.kyoto-u.ac.jp/~motizuki/Inter-universal%20Teichmuller%20Theory%20IV.pdf
[4] Inter-universal Teichmuller Theory IV: Log-volume Computations and Set-theoretic Foundations. (2020-04-22)
P67
Section 3: Inter-universal Formalism: the Language of Species
In the present §3, we develop — albeit from an extremely naive/non-expert
point of view, relative to the theory of foundations! — the language of species.
Roughly speaking, a “species” is a “type of mathematical object”, such as a
”group”, a “ring”, a “scheme”, etc. In some sense, this language may be thought of
as an explicit description of certain tasks typically executed at an implicit, intuitive
level by mathematicians [i.e., mathematicians who are not equipped with a detailed
knowledge of the theory of foundations!] via a sort of “mental arithmetic” in the
course of interpreting various mathematical arguments. In the context of the theory
developed in the present series of papers, however, it is useful to describe these
intuitive operations explicitly.