If I have an idea, you can argue that it exists in the biochemical stew that is my brain. If I share that idea, whether it be through speech, through writing, or through smoke signals, it now has an existence that is outside a person or persons.
Where? Where do shared ideas exist?
Related questions: Where do ideas come from? What is an idea? What does it mean to share something?
Okay, so there’s the physical “space” that houses an idea. Such as print or other media. And then the idea exists in people’s brains. But what’s more interesting to me is in the way an idea, once shared, changes. So, you tell your idea to someone. It’s then heard / ingested by that second person, and is then the idea is re-shaped, edited, built upon, by a second person. It is experienced, interpreted (or misinterpreted), thought about in a way that’s different from the first person’s experience of the idea. This is where miscommunication can come in But it’s also where very interesting collaboration can come in. I don’t think the same exact idea is experienced by two people. Our brains, our individual experiences, our interpretations, are always going to make the same idea into two different ideas.