First picture is of different people debating some pieces of knowledge. No one could claim reliability for a certain piece of knowledge. These people must go on discussing about their knowledge. Some knowledge could be proven wrong.
You could not prove something to be true knowledge, but you could prove it to be wrong. Hume has some words on this scepticism.
The pluralism is needed to discuss knowledge and to discover and weed out unreliable knowledge.
I need to think this over,
(picture: Hume (Wikipedia)