I own a house. In what way? The land registry says that I do. If it starts saying something else, then I don't. The police and courts will make it real.
My wallet is only mine because that's what we agree.
The brand Coca Cola is just information. But if you start selling your own under their brand you'll find out just how real intellectual property is.
Everything is society is only real because we make it real. "Ownership" isn't any more or less real of tangible or intangible things.