Why is "We are not eating the pears" wrong? Is it just the "the"? So far there didn't seem to be a difference between things in general and a specific thing in Czech. Or did I miss something?
There is a difference and most often Czech does use a demonstrative pronoun (ten, ta, to, ty...) to point to specific objects.
There is some very specific situation, where one could translate it with "the" imaginable, but it is really quite artificial, and would make it pretty confusing, if accepted.