I could never, for the life of me, recall the definition of a root system in Lie theory. It probably doesn't help that I've never taken a course on Lie Theory - the algebra, or the groups, or the differential geometry - even though I was at one of the best universities at the country. But then again, I was young, and had much else on my mind, like a mother who had been driven insane by the theft of her property. Which might explain my sympathy for the Palestinian cause. But doesn't, because that is, like the former, simply a question of justice. 


The definition of a root system, I find - if not others, is easily forgettable. However, recently I discovered that root systems were an example of a quandle, the axioms of which go back to Mituhisa Takasaki in 1942, and simply axiomatise the properties of conjugation in groups. I found this useful nugget in the book, *Quandles, An Introduction to the Algebra of Knots* by Mohammed Elhamdadi and Sam Nelson. 

Would it then, not be useful, to include this in a discussion of Lie algebras and their classification? 

**edit**

@Noah Schweber: I've seen papers that relate personal anecdotes. For example, a paper titled *Much Ado about Nothing* on the zeros of some system. If it's good enough for them, it's good enough for me. 

@Darij Grinberg: A typo...that's easily fixed. Who are you insulting? That's not what I'm asking here. I'm curious about how to make mathematics easier to learn, similarly as Voevodsky was. Important precedent.