Edit: By “first”, I meant “oldest”, my bad guys. Reddit really should give us the option to edit the titles
It's a complicated matter, made even more so by the inherent difficulty of psychoanalysing a long-dead person from a wholly different cultural background at a distance of years or centuries. u/Iphikrates examines the matter in this post, while u/hillsonghoods has a Monday Methods post on just why it's so complicated.