The sun doesn't rise, the earth rotates. For eons humanity conveniently arranged its workdays without difficulty arising from the inaccuracy of this notion. Likewise for light and darkness. So long as we deal only with the results of either, there is no difficulty with these abstractions. But when we attempt to deal directly with darkness, rather than the results or effects of the darkness, then a serious problem arises.
Light actually exists.
Darkness actually does not exist. Evil is merely a generally convenient mental abstraction signifying the relative absence of good or goodness. So long as we are dealing only with the results or effects of either, no difficulty arises. But when we attempt to deal directly with either, it becomes crucial to determine whether both actually exist, or one is merely a mental abstraction signifying the relative absence of the other. And evil or badness cannot thus or otherwise be actually sensed.