Nearly all PhD programs in mathematics in the United States begin by requiring students to pass some set of preliminary or qualifying exams to demonstrate they have a knowledge of the fundamental subjects of mathematics. They usually must be completed in the first two years of the PhD program, and at some schools they purposely serve as a tool to "weed out." students.
As someone currently in a first year math PhD program, this is my life right now. Literally the only thing that matters right now is passing these exams. Thankfully, I am at a school where I have multiple chances to pass these exams, and which do not construct them to purposely remove students from the program. However, I have still found it to be an overwhelming culture shock. And in x+y, Eugenia Cheng has given me the language to express what I have been trying to for months.
Coming from a small, liberal arts college, I was struggling with the mental shift that has been required for me to be successful on these exams. I have learned that, essentially, the way to pass the exams is to memorize as many things as possible. You can have a perfectly fine fundamental understanding of the concepts, but because you are only asked to solve problems which you have seen before, literally the only way to pass these exams is to have the mental recall of solutions which you never would have come up with on your own. There are little to no problems where you "follow your nose" to the answer by applying the fundamentals. Instead, you just have to memorize all the critical proofs.
This has irked me because personally, I do not consider mental recall to be a huge part of being a mathematician. Yes, you should have an understanding of the basics, especially in your chosen field, because you don't want to always be looking things up. You want to just know things. But in my experience, the knowing things comes from using them over and over, not from purposely memorizing them. And in the end, you can always look things up. It also bothers me because I feel the skills that my undergraduate education focused on - collaborative mathematics, how to write proofs well, how to present math to experts and non-experts, and, most importantly for actual math research, problem solving - don't matter in this system at all.
Cheng explains that the educational methods which focus on tests and memorization are ingressive, a term she coins to refer to aggressive, competitive, and self-centered behavior, while the undergraduate education I received was ingressive, a term to describe behavior which is more collaborative and community-focused.
The main thesis of x+y is that we have been mapping character onto gender, and in order to actually fix gender inequality, we need to quit thinking about gender and think on a different dimension: that of ingressive and congressive character.
As a gender expansive person, I was initially concerned Cheng would simply be replacing one false binary with another. And while she does hedge that everything is a spectrum and nothing is binary, it still felt at times that she was treating it in that fashion. However, I can't deny that the idea of thinking on a completely different dimension from gender is appealing. And Cheng is unflinchingly inclusive, repeatedly bringing trans and nonbinary people into her discussions of gender, and she demonstrates a large amount of intersectionality, speaking at length how being a person of color can affect relationships with gender, and the discrimination people face.
And while I have my qualms about the book (Cheng seems to say that we need to convert all the ingressive things in our society to congressive things, which is a point I am skeptical of as someone who feels that there must be a balance to things) I cannot deny that this language has been incredibly useful. I would genuinely love for the terms ingressive and congressive to catch on (maybe in the math community at least they will?) because I find them to be an illuminating and productive way to describe the world around me. I would definitely recommend this book to anyone, math nerd or otherwise, who is interested in looking at the world through a new lens. Or, should I say, in a different dimension.