I work with a number of younger software engineers, so occasionally I’ll say something that demonstrates a sizeable generation gap. Usually it is because I’ve mentioned the lyrics of a song from the 80s, or some early 80s television show.

The other day I found myself more than a little surprised. I was explaining something to some of the boys, and at the end of my explanation I said, half in jest, “QED“. The conversation that followed went like this:

SE1: “What’s QED?”

Me: “Hey?”

SE1: “What does QED mean?”

Me: “What the? QED. You know, abbreviation for a Latin phrase that means something like ‘it has been demonstrated'”

SE1: “Hey?”

Me: “Used at the end of a mathematical proof! Come on – you studied Maths at Uni!”

SE1: “Maybe you used it back in the 1940s when you were at Uni!”

Me: “Hey? What the hell did your lecturers use to indicate the end of a mathematical proof?”

SE1: “Der – we used the EQUALS sign. Maybe you’ve heard of it?!”

Ok, we laughed a lot – the conversation was quite funny. But I was also disturbed by it. I kept thinking about it and mumbling “QED? What the?” a lot. Then I said something like:

Me: “I can’t believe it. What are they teaching kids at Uni these days?”

SE1: “Sure, back in your day, after you used your abacus to calculate something, I bet you wrote down ‘QED'”

Yes – I get it…I’m old. 38 to a 25 year old must seem ancient. Hilarity all round.

So, I asked two other younger software engineers. They also didn’t know the phrase! So on to Instant Messaging, where I spoke to another software engineer at another company who knew me and the younger guys in question. He is a little older than them, and clearly a little wiser (he knew the phrase). His response to me was this:

SE2: “Don’t be too hard on them – they did study at RMIT after all”

Sorry to spoil the sample, but I’m 26, and went to RMIT, and of course I know what QED means! Do they not teach this at school any more?

Ah, the good old days….

QED – Latin version

Quod erat demonstrandum

(that which was to be demonstrated)

QED – alternative version

quite easily done

I suppose they no longer use the ‘therefore’ symbol either (three dots in a triangle arrangement) or the

‘for all’ symbol (upside down A)

This is probably the thin end of the wedge (or the apex of the cone?). Soon the mathematical language will become as derelict and grammarless as spoken English.

It took me a while to realise but my Yr11 Maths teacher last year used it once or twice. He did explain it but most of the class must have had (and some still have) brain damage or something.

Concerning the ∴ symbol; yes it is still used. Very useful.

But I’ve never heard of a “for all” symbol.