Art is an idea

Most [clients] expect experience design to be a discrete activity, solving all their problems with a single functional specification or a single research study. It must be an ongoing effort, a process of continually learning about users, responding to their behaviors, and evolving the product or service.

Art is an idea that has found its perfect visual expression. And design is the vehicle by which this expression is made possible. Art is a noun, and design is a noun and also a verb. Art is a product and design is a process. Design is the foundation of all the arts.