Mathematics Without Numbers (1959)

I think the biggest mistake people make when thinking about mathematics is that it is fundamentally about numbers.

It’s not.

Mathematics is fundamentally about relations. Even numbers are just a type of relation (see Peano numbers).

It gives us a formal and well-studied way to find, describe, and reason about relation.

Vast piles of mathematics exist without any relational objects, and not exclusively in the intuitionistic sense either. Geometers say it's about rigidity. Number theorists say it's about generative rules. To a type-theorist, it's all about injective maps (with their usual sense of creating new synonyms for everything).

The only thing these have in common is that they are properties about other properties.