“The single slit shows no interference with the nonexistent other slit, which of course it can’t. That’s no mystery.”
The subject of my response to Steve was that single slit patterns was wave behavior. I only added the statement about interference to show that was the difference he was seeing. Not that one was particle.
Yes to be fair a single slit will not show an interference pattern. So one might think there is no wave function present but the experiment itself sort of eliminates anything that would produce an obvious wave pattern.