I was somewhere on Twitter looking for reading recommendations -- which seem to be harder and harder to find -- and came across a tweet, linking to an essay, arguing that cursive writing was obsolete and should be replaced with architectural lettering.* While it was serious, it was not intended to be an obnoxious claim, so I will leave it in a graceful anonymity. Like most claims about something being obsolete, it's simply untrue that cursive is obsolete; use of it has undeniably declined but there are still large numbers of people who use it on at least a semi-regular basis, and certainly more than use architectural lettering (which I would suspect is itself undergoing a much steeper decline as the primary people who use it have increasingly shifted to using computers). Most claims about this or that being 'obsolete' are expressions of a wish rather than descriptions of a fact; people don't go around proclaiming in public that the 5-1/4 floppy disk is obsolete, because it genuinely is obsolete, and almost nobody even thinks about it much at all.
But it all led me to think of other cases. When I was growing up there were people who would argue that pen-and-paper was obsolete because now we had calculators. As far as I can tell, the result of educational programs in which calculator was substituted for longhand calculation was not an increase in people who could do advanced mathematics, but an increase in people who can't do even ballpark estimation of fractions or percentages, whether in their heads, on paper, or with a calculator, because they never actually learned how any of it works. (As a perhaps-unfair contrast, I don't know if anyone is doing it today, but for years one of the most lauded college computer science programs in the world had its introductory students doing everything with pen and paper -- you weren't allowed to use a computer, you had to do all the computing on paper in a particular format that kept track of the various computing functions, so you'd write your program, and calculate and follow the numbers through every step of the diagram-machine. People swore by it, because students didn't just learn a program language; they learned exactly what their programs did.) And other uses of 'obsolete' to argue about some educational program change crowd to mind.
I think my view of it all is this. You should not trust anyone trying to convince you that anything learnable is obsolete; this is a term that is only appropriate to tools with very specific purposes. Moreover, I think that if you are actually teaching it, it is not obsolete. If people are learning shorthand, shorthand is not obsolete. If people are learning Old Norse, Old Norse is not obsolete. If people learn how to build a steam engine, steam engine design is not obsolete. If people are learning it, it is not obsolete. And part of this is that, if you can learn something, you genuinely have options now that you wouldn't have at all if you didn't. If you keep up your learning of it, even if only by refreshing your memory, you continue to have those options. Maybe you'll use your Boyd's syllabic shorthand or your Gregg shorthand, and maybe you will not; but as long as you know it, it is not obsolete, it is just, at most, uncommon. Perhaps it stops being mainstream and becomes a hobbyist's field, perhaps it becomes less a general field and more a specialized one, but there is no sense in which it is obsolete. What can be learned and retained has no obsolescence.
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* Besides obsoleteness, the other criticism of cursive was that it is so often illegible. I confess I've never understood this criticism. Precisely one of the points of cursive is that it lets you literally scribble things down. Cursive, unlike printing, is highly flexible; when scribbled it is a poor man's shorthand and when prettied-up it is a poor man's calligraphy; its range is not infinite, and its scope does not fit every situation, but it is an excellent demotic. It's like sketching; you don't need blueprint-precision for most needs, you just need to be able to throw down some lines that people can more or less understand. It would be absurd to say that sketching should not be taught because it is not drafting. In my own case, I tend to print notes and scribble first drafts of poems and things in cursive, and this works beautifully. Even when printing, I use cursive as italics. There are lots of things you can still do with cursive, even without being careful about penmanship.