In my limited experience, the “hard problems” in philosophy are the problems which are either poorly defined and so people keep arguing about definitions without admitting it, or poorly analyzed, so people keep mixing decision theory with cognitive science, for example.
See also how many of the comments in this thread amounted to “if by sound you mean ‘acoustic wave’ it does, if you mean ‘auditory sensation’ it doesn’t”.
See also how many of the comments in this thread amounted to “if by sound you mean ‘acoustic wave’ it does, if you mean ‘auditory sensation’ it doesn’t”.