Quantum Limits of Knowledge 2021 Tuesday 30th March, 2021 Users of a physical theory are themselves part of the physical world. This obvious fact leads to a requirement on any physical theory that is supposed to be universally valid: The theory must be able to correctly describe the users of the theory. Quantum theory (assuming it is universally valid) thus imposes limits on our knowledge in two different ways. Firstly, when we use quantum theory to describe an experiment, we obtain constraints from the familiar Heisenberg uncertainty relation. Secondly, when we take into account that the process of using quantum theory is itself a quantum mechanical process, we encounter 16 other, less familiar, limits. In my talk I will try to shed some light on this second aspect, which is much less well known than the first.