This question caught my attention like a snagged fingernail, and it's still pulling at me: here's my first cut at an answer. I'm taking the no-writing parameter seriously as a limiting condition: what level of technological society can emerge in conditions which preclude writing—for example, if it's forbidden for religious reasons? I'm going to treat this as holy writ for purposes of this thought-experiment: rules-lawyering around the no-writing rule in the comments will be treated as Derailing and deleted, with one special sort-of-exception which I'll explain near the end because it opens up a bunch of interesting consequences.

Question for you: One HN thread caused me to wonder about this: What would a technological society look like that somehow managed to side-step the written word? Would such a thing even be possible? If not why not?

My rule of thumb answer is: it wouldn't be possible for human beings to develop a technological civilization—at least anything beyond roughly 17th century levels of energy utilization and mid-19th century levels of agriculture—without some form of record-keeping technology. And without writing they might never get that.

The reason is memory capacity. Yes, we can memorize lengthy texts when assisted by verse metrics as a form of mnemonic—the Iliad and the Odyssey, the Koran—but the format is error-prone, transcription is at least as time consuming as copying a mediaeval illuminated manuscript, and the "books" are high maintenance (they need food, clothing, and shelter). I don't know how many books one human being can memorize, but even if the number runs as high as two digits (which I think would require a very rare level of memory) you're then faced with the problem of what to do if one of your books gets cancer or dies of old age. So not only is copying more expensive than in a mediaeval monastery's scriptorum, but the substrate onto which "books" can be copied is extremely expensive (because we're coming at this from a pre-industrial situation where agriculture is labour-intensive because there's no copious supply of cheap energy). To put it in perspective, if one "book" can memorize five texts, then those five texts represent an entire productive human lifespan's worth of opportunity costs.

We know you can get to high-level neolithic culture (including agriculture and settlements) without writing, because our ancestors did so. I'm guessing that by using a monastery system for libraries, you could maintain stores of expertise equal to a couple of hundred (maybe as many as a thousand) "books". But studying them would require a scholar to travel to wherever the nearest current copy of a "text" lives and listen to (and memorize bits of) their recitation. Carrying on an actual academic dialog between two or more texts would be ... interesting, but likely slow, and the cost of creating a new text would be enormous (human lifespan-equivalents).

And then we run into mathematics. Assuming they figure out binary, integer arithmetic on fingers and toes gets you a long way for basic counting, multiplication, and optionally subtraction and division. But I'm not sure how they'd explore reals, let alone algebra or calculus, in a notation-free environment. I imagine tally sticks might work if our sophonts have opposable thumbs, but then we're cheating and getting into writing systems by the back door.

We might have specialist memory folks whose job is to act as temporary stores for working human calculators, but again, that's going to be a rare skill ("Quick! Memorize these six thirty digit binary numbers! Now repeat the fourth and sixth back to me!").

So I see the natural sciences stalling out around the point where they'd be getting to Newton/Liebnitz, and as for literature, oh dear. (Hey, I'd be out of one job but into another as an itinerant storyteller, with just one story to call my own, endlessly elaborating on it. I'd go nuts!)

Law and arbitration is going to be problematic. The Mediaeval Icelandic parliament is said to have started each session with a recitation of the legal code; any law that no sitting legislator could remember was deemed to have passed beyond the sunset. This is thus shown to work, after a fashion, for non-literate societies up to a mediaeval level. However, reliance on memory means that a case-law system simply can't develop, except in the sketchiest of ways. (On the third hand, though, one might expect the accounts of witnesses in such a memory-based society to be more detailed, if not more accurate, than what we've become used to.)

Economics is going to be even worse. Pace Graeber, money may have originated as a tally mechanism inside temple grain stores: you can't eat gold, so it serves as a persistent token representing so many sheaves of wheat or ewes or whatever that the temple has received on your behalf. Money represents a debt. But without hard records outside of someone's head, how do we agree on exchanges of fair value? There are possible work-arounds, such as using an impartial third party as an arbiter, or using gift-giving rather than purchase-buying, but they probably don't scale well.

As for engineering, I think they'd have to rely on models and finger-in-the-sand sketches. You can get quite a long way with that; I live on the top floor of an apartment building where about 80% of the builders would have been illiterate when they constructed it. (Admittedly without electricity, plumbing, or central heating at the time of construction, circa 1829.) You might get low-pressure walking beam steam engines, but I don't think you'd be able to build high pressure steam engines (and thereby prime movers) without being able to mess around with the ideal gas law and do heat transfer calculations—it's too dangerous (the failure mode is an explosion and your research notes are mortal), and if you build in conservative margins of error on stuff like the boiler wall thickness you'll end up with it weighing too much to be useful.

The lack of steam traction means agricultural productivity will remain geared against human and animal labour: by our standards, it's very labour-intensive indeed. I don't see the lack of writing as precluding the development of things like threshing machines—and in related industries, the Spinning Jenny and the weaving loom—but lack of motive power and recording technology may prevent more complex derivatives (such as the Jacquard card-controlled loom). Clothing is going to stay expensive for a long time here. In general devices which have hidden dependencies on high pressure engineering aren't going to be readily available: I'm guessing the sewing machine, developed in the mid-19th century, would in principle be possible but mass production of standardized steel needles and precision components would make them inaccessible.

... This is as far as the discussion got in email, before my wife came in and made a key observation: sound recording tech is something you can do entirely mechanically. Think in terms of hand-cranked wax cylinder recorder or dictaphone: such a device is functionally equivalent to writing, albeit bulky, slow to absorb (spoken narrative is about a third to half the speed of reading), and still requiring transcription costs. Wax cylinders won't last forever, but they're easy enough to re-record by someone memorizing the "text" in five minute segments and reciting from memory. And if wax isn't good enough, there were early forms of plastic (casein polymerized with formaldehyde?) that date to the early-19th century and don't require advanced chemistry which might do as a shellac alternative in mass use, if indeed shellac itself isn't available.

So, if we permit audio recording as a possibility (but not writing as such) we then have the derivative question: can a civilization develop to wax cylinder reorders in the absence of writing? (Note that this technology is not trivial: it depends on reduction gearing, probably an escapement mechanism, and some degree of precision engineering. It also almost certainly depends on your being able to deliver division of labour which is itself a question of economics and resource allocation which, under conditions of expensive information storage, is problematic.) And, if that isn't a leap too far, how much further can you bootstrap your technological civilization if you can do some audio reording? And what will such an a-literate climax society look like?