https://www.theguardian.com/books/2020/jul/22/x-y-by-eugenia-cheng-review-an-end-to-the-gender-wars

A bold and optimistic theory of gender and cooperation, based on the insights of maths

Eugenia Cheng is on a mission to change the world for the better, using maths. Her first book, How to Bake Pi, used recipes to teach readers how to think mathematically. The Art of Logic, published in 2018, was about using the principles of mathematical logic to have more productive arguments. x + y is an even more ambitious project, the aim of which is to end the gender wars and create equality by building “a whole new theory of people”.

Cheng begins by addressing why it is unhelpful to associate characteristics with gender, and explains why “leaning in” and “positive discrimination” both fail to fix inequality. She proposes a solution based on her specialist subject of category theory, which is more interested “in describing things by the role they play in a context, rather than by their intrinsic characteristics”. Mathematically, she says, “if we have two things that are not equal, we could make them equal by making the lesser one greater or by making the greater one less ... However, there is a completely different way we could do it, which is by evaluating the two things on a new dimension entirely.” Cheng insists that proper maths, the fun kind, is not about being right, but is a way of thinking differently, and that includes exploring ideas that are impossible according to existing rules. It’s a way of seeing this exhausting debate from a completely new angle.