Just a Matter of Knowledge?

Abstract

There is, it seems, a rather natural response to the conceptual problems raised by QM. This response, put frankly, is to say that ‘it’s all just epistemic!’ More precisely this would mean to deprive the quantum state of its ontological significance and to construe the theory not as a description of the actual, real situation of physical systems, but rather as a representation of the knowledge an actual or ideal observer or agent has about these. So for instance, when a quantum system passes a double slit, we cannot know exactly where it is going to turn up. But we can try to make precise predictions about its future behavior, based on our previous experience with similar situations and systems, and hence quantify, in a sense, our knowledge about its future behavior and about the occurrence of spots in various regions on the screen behind the slit. Again given past experience, a quantum mechanical state function may be the tool of choice to accomplish this task. But in the instant we see a dot appearing on the screen we can update our knowledge about the system’s actual state, since we can now be rather certain (assuming that we have not visited too many epistemology classes) that the system has occupied exactly that region on the screen at the moment of the appearance of the dot.