Hello, AskHistorians!
I saw the FAQ and questions here regarding English, but what about French?
I am a native French speaker and I am curious how far I could go back in time and still be understood. I am a literature buff and philosophy graduate student and in my readings, I have come across 16th century literature (François Rabelais) and was able to read it. But could I go further in terms of written French? And what about spoken French?
Thank you!
You could also try asking this question in /r/linguistics; I'm pretty sure they have a number of historical linguists there.
I don't think that the intelligibility of old texts would make the best indication of whether you could understand historical French speakers. Writing tends to change less over time than spoken language almost as a rule. Since 1500 French has undergone many vowel shifts and other changes (like not pronouncing the "x" in the phrase "dix pommes"), but the spelling of most words has remained the same and disguises these changes to the modern reader.
Another issue with French, or any European "national" language, as one goes back in time is that regional and dialectical variations used to be more extreme. You'd probably have better luck in Paris, whose dialect had the heaviest influence on Modern Standard French, than in other parts of France whose dialects have been partially subsumed by standardization.