Yes, agreed. Unless they were ever only sailing short distances and only in their local near-coastline seas (and very local - as soon as you start looking at th

Yes, agreed. Unless they were ever only sailing short distances and only in their local near-coastline seas (and very local - as soon as you start looking at the sun, moon, stars and planets to get some idea of where you are it's pretty much impossible to not understand that you're not on a flat disc). As for illiteracy - it's not always necessary to be literate in order to know something. In our modern world there's a great many things 'everybody' knows, without necessarily ever having read about it. True things as well as false things, obviously.