The proposition believed by Lorites is that every idea has already been thought of.
Ironically, one of Saunt Lora's fids proved that the proposition itself had already been thought of.
Possibly a reference to Ecclesiastes 1:9 from the Old Testament:
"The thing that hath been, it is that which shall be; and that which is done isthat which shall be done: and there is no new thing under the sun."