*
!.gitignore
!init.el
2. The reason I prefer ~/.emacs.d/ is that I have it in a git repo and on every system, I'll just clone the repo and soft link it in the home directory. This way, I have only one directory inside home about emacs within which my files are explicitly separated and tracked.
i. Peano Axioms: (Typically) your initial element is 0 and you'll get 1 by applying the successor function to 0 and 2 by applying that to 1 and so on.
ii. Von Neumann's definition of Ordinals: {} is zero and one is {{}} and two is {{}, {{}}} and so on.
iii. Conway's definition of Surreal numbers: {|} is zero and { {|} | } is one and so on.
iv. Church encoding
and many more.
P.S. I'm not a logician and don't know whether "more of an abstraction" has any well-defined meaning and not just the meaning that might be inferred by a software developer.