Literally all of software is artificial? Being explicit and reasoned about how you choose to allow or deny a particular computation is, surely, at the heart of a lot of computer security?

With that logic you could call SQL injections a natural feature of database management systems. If a general purpose system starts dropping tables or messing up numbers in a report just because that string was in the text it read, that system isnt worth a damn in the enterprise sector

> Separation of instructions and data is artificial. Reality has no such separation. A general purpose system needs not to have them either; it's a design feature, not a bug.

Note: I'm parsing 'needs not to have them' as 'needs (not to have them)'. If you were using 'needs not' as an alternate for 'does not need' then never mind, although I'd guess that is not the case because the alternative for 'does not need' would be 'need not' rather than 'needs not' and you probably wouldn't make that mistake.

Doesn't this imply that it is not possible to implement a general purpose system on any of our current computing devices?

For all our current computing devices everything that can be done on devices that do not separate instructions and data can also be done on devices that do, and vice versa.

A pure Harvard architecture machine has exactly that separation. Admittedly, there needs to be some mechanism for converting data to code so you can actually program it, but it doesn't have to be accessible by the device itself. E.g. programming the Microchip PIC16 series of microcontollers required driving the reset pin to 13V (enough to destroy any other pin). It's not possible without dedicated external hardware.

Only in systems that need to be themselves super generalist. Which is almost never the case.

If you hand me two sheets of paper, one of them containing instructions and another containing data, I'll have a pretty easy time keeping them separate, and I think most humans wouldn't struggle with that problem either.