In my Plum Blossom Divination course, I wrote:
Before the Yijing was written, the concept of Yi already existed. It might not exist in the minds of people. It might just be floating in the Universe waiting to be picked up by someone living on earth.
However, when one picks up an idea floating in the Universe and writes it down as his discovery, it is considered his idea. Obviously he cannot quote the source of the idea.
Yes, nothing is new under the sun. But if you are the first one to discover something, how can you quote an "authoritative source"? Note that you do not create anything. You just discover something that already exists but is unknown to people before your discovery.