What Makes a Problem?

I ask you now ladies and gentlemen. What on earth makes a problem hard? If you think about it, it just doesn't seem to make much sense. two plus two, that's an easy problem. What gives energy mass, that's a different story. I can't help but wonder weather some deep truth about complexity relies on the bases of complicated problems. I mean, what the hell else would it rely on? The cost of condoms in china? (doubt it) If problems seem harder than others based only on our philological perceptions then two plus two really isn't any harder than what gives energy mass. Definitely something worth thinking about.