There are lots of ways to explain the interference pattern. Probably the most famous "renegade" theory is Bohmian mechanics, which suggests that there's a real

There are lots of ways to explain the interference pattern. Probably the most famous "renegade" theory is Bohmian mechanics, which suggests that there's a real particle that is guided by a wave that we can't see. The particle doesn't interfere with itself, but it's guided by a wave that does. I don't think the particle can select a path from a set at the time it's fired. That sounds very much like a local hidden variable, which is more or less strictly ruled out by violations of Bell's inequality. Unless you allow causality to go back in time (in which case, it can make its decision on where to land based on, for instance, how it will eventually be measured). You can do things to the particle (like trying to measure it, or entangling it with other particles and measuring them, etc) which make it seem less and less likely that the particle could have selected a "which-way" as it was fired. For instance: suppose you put a detector on one of the slits as the particles are "in flight". We know this results in no 'interference pattern' observed. How do the particles know to scramble themselves as soon as the detector is put on? It doesn't seem like a local effect, since all the particles that go through the other slit never interacted with the detector at all and therefore shouldn't have been affected. But they are anyway. So either there's some information being passed back in time along the particles' history, or there's some strange nonlocal effect.