20th century Cantor:

All mathematical objects can be defined as sets.

Fundamentals:

  • numbers
  • permutations
  • partitions
  • matrices
  • sets
  • functions
  • relations

Geometry:

  • hexagons
  • points
  • lines
  • triangles
  • circles
  • spheres
  • polyhedra
  • topological space
  • manifolds

Algebra:

  • groups
  • rings
  • fields
  • lattices