The relationship between Intelligent design and science has been a contentious one. Intelligent design (ID) is presented by its proponents as science and claims to offer an alternative to evolution. The Discovery Institute, a politically conservative think tank and the leading proponents of intelligent design, launched a campaign entitled "Teach the Controversy" which claims that a controversy exists within the scientific community over evolution. The scientific community, however, states that there is no controversy and rejects intelligent design as creationism due to ID proponents' lack of peer-reviewed research and the scientifically undefined quality of observable intelligence.