Dante Turns Seven Hundred and Fifty
newyorker.com
newyorker.com
To put this into perspective, Chaucer was two generations after Dante, and his writings are _barely_ comprehensible by layreaders. Here's a bit of the prologue of The Canterbury Tales:
And specially from every shires ende/ Of Engelond, to Caunterbury they wende,/ The hooly blisful martir for to seke/ That hem hath holpen, whan that they were seeke.
https://www.youtube.com/watch?v=bGVDeafmsco
http://www.kami.demon.co.uk/gesithas/readings/bss_oe.html
And a good argument can be made that Shakespeare has a non-trivial percentage that's also not comprehensible to the modern reader/listener. And that was 16th century!
However, I agree that between Shakespear and the King James Bible's influence, that's about as far back as a Native English Speaker can go and generally understand what's going on. Much of it is attributed to the "Great Vowel Shift" in English https://en.wikipedia.org/wiki/Great_Vowel_Shift
It's amazing what important literature can do to "fix" language.
It seem remarkable that so much linguistic change can happen in such a relatively short time period, but my wife points out that in her home country of Korea, the original 15th century text that introduced their written language (Hangul) is not readable by modern Korean readers (slight differences in orthography from the modern Hangul notwithstanding).
[1] Don't be surprised. Take for example Urdu, the language spoken in Pakistan and large parts of Kashmir. It is an entirely artificial language, based on Pashto and Farsi if I recall correctly, that was imposed some 200 years ago by the British Raj <http://en.wikipedia.org/wiki/Urdu#Origin> as a political decision to submit the local population.
To clarify: Urdu is primarily Hindi, Arabic, and some Farsi. I don't speak any of those languages, but from what I understand, those are the primary components. Pashto is a more minor one. which has had an influence on the language due to the large number of native Pashto speakers in Pakistan.
Also, most of what you said is correct, but to anyone reading this, that Wikipedia page is unfortunately rather misleading. It's not exactly wrong because Hindi itself is so heterogenous that it should honestly be considered multiple languages. But it says that Hindi and Urdu are mutually intelligible, which is misleading. Really, a more accurate statement would be that "some speakers who identify their language as Hindi are able to understand Urdu". Many Hindi speakers[0] would not be able to understand Urdu; many have difficulty even understanding other Hindi speakers.
For example, most of my family speaks fluent Hindi[1]. However, none of them can actually understand Urdu except the ones that also happen to speak Arabic (because they lived in Arabic-speaking countries for a few years). It's like how English speakers may be able to pick out some German words, but not actually understand the language when spoken, whereas learning Dutch might help them bridge the gap.
This is similar to the situation with Arabic, which we treat as a single language, but is actually a spectrum of many different languages that are partially (but not always completely) mutually intelligible. It's hard to explain this by analogy to English speakers, unfortunately, because English dialects are relatively homogeneous by comparison[2].
[0] and I'd be willing to venture most, though it depends very much on which regions and religions you survey
[1] Again, to be precise, this means that they use the name "Hindi" to refer to the language that they speak.
[2] which says more about what we classify as "English", which is a political decision rather than a linguistic one, which brings us back to the original point all over again.
Dante's Inferno is truly scathing and quite gossipy. Such bitterness would transition well to the current ecosystem, methinks.
[0] Or any SV old time luminary, really. I pick Doug because of his visionary potential.