Art is partly about drawing out feeling. Contemporary art is often the search to find another way to express an object, idea, or concept other than the way it is usually visually represented. For example, if someone wants to portray a dog, the artist might paint a tree with a dogpile at the foot of it. Not only does the viewer think “dog” but it also erupts feelings about the dog, such as annoyance that a dog just ran havoc through their yard. If the artist were to just paint a dog, there likely would be less feeling elicited on the part of the viewer. Art is about drawing out feeling.
Often artists try to convey concepts, such as unemployment, and since concepts are not concrete, they require creativity to pull off the representation (see Unemployment, below). So that makes sense that you’d have to stretch the imagination. But the other mental exercise in composition is to take something that already exists in a tangible form, and figure out how to invert that tangible object, so that you get a concept (see Garden Print below). So in one case, artists are taking a non-tangible object and making it tangible, and in the other case, they are taking a tangible object and making it non-tangible.