Teaching - Art or Science?

I think I am going to have to cheat and say that on some level I believe teaching to be both an art and a science.  We have certainly seen how the study of different learning theories and the ways in which individuals learn and understand can definitely be grasped on a scientific level.  But once that process is understood, the real art of the practice of teaching takes over.  Understanding the tools at hand, the instructor must now develop the course work on top of the over-arching principles.  The science provides the foundation, but the art is the source of the rest of the structure.