While it's autobiography rather than fiction, the Confessions of St. Augustine explore the author's state of mind as deeply as any modern work I can think of. I

While it's autobiography rather than fiction, the Confessions of St. Augustine explore the author's state of mind as deeply as any modern work I can think of. It was written around the end of the 4th Century AD. [0] But this article started with an example from the middle ages rather than the ancient world, so lets look there as well. Medieval literature does explore human feelings quite deeply. The stories of Chaucer (Canterbury Tales), Dante (Inferno, etc.), and Boccaccio (Decameron) exhibit characters with a rich internal life. Arguing to the contrary mostly proves you have not read them. [0] https://en.wikipedia.org/wiki/Confessions_(Augustine) https://en.wikipedia.org/wiki/Confessions_(Augustine) (Edit, left this out.)