> Going by dates of introduction to determine if a math topic should be part of general knowledge doesn't make sense. On one hand, yes, and that’s part of the

> Going by dates of introduction to determine if a math topic should be part of general knowledge doesn't make sense. On one hand, yes, and that’s part of the point I usually make when I recite how far into the standard university course Newton’s or Gauss’s knowledge can still be found. On the other hand, no, and that’s the other part of the point I want to make when lamenting high-school maths, because the state of the art there is obsolete to a level that’s patently insane. Thank you for making me think about this. I’ll put it like that. How often do you change your mind? (Or, if you want: how often do you make breaking changes to your APIs?) Obviously it makes to sense to keep a running tally and decide whether to do it or not depending on which side of the target value you’re currently on. Making a performance indicator out of this is a sure-fire way to end up in a completely twisted universe. On the other hand, if you do it all the time something’s equally obviously gone awry—maybe you just started out being very wrong, and that’s not a problem with the current you, but if after some time there’s still no signs of settling you need to do some soul-searching. Similarly but even more dangerously, if you never do it, it’s of course possible you were simply right to begin with, and that’s happened once or twice in history, but you must seriously consider that you might either be living among fools or avoiding the intrinsic discomfort of the process and thus a fool yourself. I’d say the recency of a general-education syllabus is an indicator of a similar nature: meaningless in each particular instance, and emphatically not to be used as a target metric, but at the same time as the average goes into the margins it’s increasingly likely it’s failing at its job. And by that measure maths is universally in deep shit. (The natural sciences are as well, just with more variance; I’m not qualified to judge the rest.)