"With the fate of Schrödinger's cat in the balance and Heisenberg's idea that quantum theory only describes observations, Rovelli inevitably asks the tricky questions: what is observation? What is an observer? ...He is the champion of the "relational" interpretation... [that] quantum theory does not describe the way in which quantum objects manifest themselves to "observers", but... how every physical object manifests itself to every other physical object. The world we observe is... better understood as a web of interactions and relations rather than objects."