Design vs Art

Intially I thoguht the interplay was simple between the two ie like Capa suggests art is using a medium to change how you see the world, whereas design is changing how we live in the world. However having read the discussion by Joshua Porter I can see how the distinction between the two becomes some what blurry, with designed objects being at an art museum and the question then being posed is the object art or design. However having read the article I feel that the distinction is although blurred there is some vague clarity in so far as a designer creates soemthing with a market in mind, ie to sell. Whereas a artist when creating true art creates it without a market in mind, the work is simply created. Thus if a painter creates work for a buyer they are hence designing and if a designer is simply creating a piece they are an artist.