We profess at each Mass, our belief in a church that is one, holy, catholic, and apostolic.
What does it mean to say our church is "holy"?
Being holy is not just being good; God created everything in the beginning and it was good. Everything is good.
In the old testament, as the first physical church structure is being established, we see men set apart as priests. Certain food offerings set aside and certain places set apart. Holiness means being set apart. Holiness means being for God.
Owning something is not the same as something being for you. There are a number of stuffed animals in my house. Legally speaking, they are mine; I own them. None of them, however, are for me. They're for my son.
God owns everything on the earth but not everything is specifically for Him. The Church - whether we refer to the physical space, the earthly family of Christians, or the mystical Body of all those in His friendship - is set apart for God. We, then, as part of that Church, are called to be holy and live lives that are dedicated to God.