Ownership is kind of a made-up topic (side note:  everything is sort of made up because that's how society and culture work).  You can say you own something because you bought it from somebody, but why did they claim ownership?  Did they buy it from someone else?  Who was the original owner, and how did they claim ownership?  We don't typically ask these questions because we all collectively believe that if you claim to own something, you own it.  If someone creates something, they can claim they bought the raw materials from someone, but then they created something new which didn't exist before then.  So that new thing is owned by the creator of it. 

This isn't the case for something like natural resources or land, especially undeveloped land.  A person can claim ownership, but the person who originally owned it merely stated a claim.  In that sense, I don't think land can really be owned.  It can merely be borrowed, to plant crops or build houses.  Which begs the question, if you're not using your land for some purpose, do you really own it?  Should you?