"And by, say, the fall of the Roman Empire, India had far more interesting philosophy ... But it turns out that Indian philosophy was heavily inspired by Greek philosophy"
That sounds very interesting. Are there any sources that discuss this in more detail? All the results on google seem to suggest that if at all a correlation exists, that Indian philosophy might have inspired Greek Philosophy.
The book I mentioned, The Shape of Ancient Thought by Thomas McEvilley, is an amazing one. That's the place to start. My now vague recollection is that the influence went first from India to Greece (via various other places) not as what I would call philosophy but maybe "speculative theology" or "speculative religion" (think Vedas, Upanishads) Then more fully formed Greek philosophy influenced Indian thought via the Hellenistic world following the Alexandrine conquests (so e.g. you wind up with Buddhist philosophy like Nagarjuna's Vigrahavyāvartanī that deploys some arguments familiar from sceptical schools of Hellenistic philosophy.
That sounds very interesting. Are there any sources that discuss this in more detail? All the results on google seem to suggest that if at all a correlation exists, that Indian philosophy might have inspired Greek Philosophy.
http://www.jasoncolavito.com/blog/did-ancient-greece-borrow-...
http://www.josephwaligore.com/greek-philosophy/indian-influe...
https://francoisgautier.me/tag/influence-of-india-on-greek-p...
https://www.quora.com/Who-were-the-ancient-Indians-influence...