yes and no.
the concept of a rose, no.
the concept of an idea/theory/thought, yes in a way. Not to say someone else might not have the same thing, but if the duplicate the image the same, I think so yes.
But is it art theft? Not really, as long as they made it their own, though if you take an idea from someone, I would at least assume you would think it needs to be changed in some ways to be your own.

Am I even making sense?

I think it depends. If you copy the concept or idea exactly, with that intention, it's theft. But I think if you just took the basic idea and made it different, it wouldn't be, or if you ended up with the same idea without knowing about the original. For example, little red riding hood. Copying it exactly, isn't really a new idea. Now, drawing what you picture it to be in your mind, or photographing the story, or writing music/poems based on it, it's taking it to a whole new level. It's been taken, but not with the intention to claim it as your own.
Otherwise yes, I think you can steal ideas, but only if you're aware of it.

if you like something you pick it up and add it to your repertoire but expand on it, it's just like metaphors and similes in writing or points of view in the world, music, and how you build your own set of principles

I think it depends greatly on what degree of theft you're talking about. If it's just the basic concept, no. If it's the concept right down to composition and details, yes.

I said no because in general I do not believe that there are any truly original ideas.
Now, there is an exception, I believe, to that: intellectual work as in a new invention (or something very similar) since an invention implies something completely new.

As far as liturature goes, I don't think there is a single new idea. It's all just rehashed stories and concepts and themes put into a new place or cultural significance. Shakespeare's Romeo and Juliet, for example) came from an Italian poem. At best, we can only write the same story as them but in a better way with more memorable characters and places and themes. Also, I've seen two writers take the same writing prompt (ideas +concept) and take it in completely different directions from each other. So, unless someone is actually plagerising (sp?) another person's words (or very nearly close to that), I do not think you can steal that kind of idea or concept.

As for art... I'm not sure where the line is drawn (no pun intended). Is it considered stealing or copying if a realist painter paints someone else's photograph? (I see this all the time, everywhere.) And then sells that painting? Does a model on DA have any say in the use of how her picture might be painted? (Or what about canded photos of people taken and sold without those peoples' permission?) What about the artists in the mall, on the street corners, in galleries that paint famous people from (obviously) photographs and then sell them? Is that stealing? Or is it not a problem because it requires a completely different type of skills set? (I'm am very curious about this because I am more of a realist painter myself.) How much of a photograph can a digital artist use before it is obvious and credit/permission needs to be given? (I don't know anything about digital art, but I am curious as it seems that there are all kinds of different disputes over this...) Personally, a lot of it seems like splitting hairs to me unless someone slaps their name on someone else's original work or actually traces another's work, which equals blantant art theft. (Although, I do see the exception for that in a lot of digital art and photomanipulations. I don't know how artists resolve those issues unless they upfront purchase all rights to the stock...)

yes you can, you could possibly not execute it the same way. But you can give your best shot at it and steal it

The idea. Other similar music proyect one years later.

Okay, so it's not about what copyright is, but what qualifies as 'stealing' and what doesn't?

Then I'm gonna have to go with a strict definition of stealing, which implies taking away. So, no. You can copy an idea, but it'll still exist in the mind of the original creator.

Maybe that's what the other person meant?

(btw I voted 'yes' because I hadn't read the other comments yet )