Although evolutionary biology is replete with explanations for complex biological structures, scientists concerned about evolution education have been forced to confront "intelligent design" (ID), which rejects a natural origin for biological complexity. The content of ID is a subset of the claims made by the older "creation science" movement. Both creationist views contend that highly complex biological adaptations and even organisms categorically cannot result from natural causes but require a supernatural creative agent. Historically, ID arose from efforts to produce a form of creationism that would be less vulnerable to legal challenges and that would not overtly rely upon biblical literalism. Scientists do not use ID to explain nature, but because it has support from outside the scientific community, ID is nonetheless contributing substantially to a long-standing assault on the integrity of science education.