Identifications, diagnoses, and treatments of pseudo-problems form a family of classic methodologies in later nineteenth century philosophy and at least partly, as I shall argue, in the philosophy of science. They were devised, not by academic philosophers, but by three of the greatest of the philosopher-scientists. (Later, the idea was taken up by academic philosophers, of course. But I will not discuss that development). Here I show how Ernst Mach, Heinrich Hertz and Ludwig Boltzmann each deployed methods of this general (...) kind, how they identified different pseudo-problems, how they gave different diagnoses of such problems, and how they suggested quite different treatments for them. I argue that it was Mach who really first developed the idea of a pseudo-problem, that he did so in a relatively focused way on the basis of two kinds of examples. Hertz’s contribution was much more limited, identifying two specific pseudo-problems concerning physics, and suggesting a way in which they might be treated. Boltzmann’s conception of pseudo-problems, though, was far less focused, being applied to a very wide range of problems in philosophy and physics. However, his conception was certainly more influential in philosophy, and perhaps ultimately more fruitful and suggestive. I argue for the originality and continuing interest of such approaches, and I try to dissociate them from any problematic ‘positivism’. (shrink)