Two arguments for more fundamental building blocks

We present two lines of reasoning, leading to elementary constituents more fundamental than the ones we know. One such arguments is new, and based on the holographic maximal bound for the number of degrees of freedom of any system. In this case, both matter and space are emergent. The other argument is old, and was given by Richard Feynman as a possible explanation of why analog systems do describe the same physics. The former argument naturally points to a solution of the information paradox. The latter argument elevates analogs from mere curiosities, to reliable tests of fundamental theories. Amusingly, the names given to this fundamental level, both by Feynman and by some of the modern quantum gravity researchers, e.g., Jacob Bekenstein, resemble each others: ``Xons'' (Feynman) vs ``level X'' (Bekenstein).
Comment: 17 pages, 7 figures, invited lecture delivered at Ninth International Workshop DICE2018, September 17-21, 2018 - Castiglioncello (LI) Italy