Are there any characteristics by which we can reliably identify and distinguish quackery from genuine medicine? A commonly offered criterion for the distinction between medicine and quackery is science: genuine medicine is scientific; quackery is non-scientific. But it proves to be the case that at the boundary of science and non-science, there is an entanglement of considerations. Two cases are considered: that of homoeopathy and that of the Quantum Booster. In the first case, the degree to which reported phenomena that (...) question established theory should be doubted arises; in the second case, the status of pleomorphism as a scientifically plausible doctrine is discussed. The application of the criterion of being scientific to these cases reveals something of the nature and density of the entanglement. (shrink)