There are two main ways to think about "hard". One of them is "not many people can do this". The other is "not many people could do this". When people disagree

There are two main ways to think about "hard". One of them is "not many people can do this". The other is "not many people could do this". When people disagree over whether something is hard, I think the disagreement usually comes down to semantic disagreement over these two definitions. Also, some people think we can get rid of the latter ("not many people could do this") because it's hard/impossible to prove. But I think both definitions are an important part of what we mean by hard, and we can't get rid of either.