On several occasions during the last eighty years, states have attempted to either prohibit the teaching of evolution in public school science classes or counter the teaching of evolution with mandatory references to the religious doctrine of creationism. The Supreme Court struck down examples of the first two generations of these statutes, holding that they violated the Establishment Clause of the First Amendment. A third generation of creationist legislation is now being proposed. Under this new generation of creationism legislation, science teachers would present so-called “intelligent design” theory as an alternative to evolution. Intelligent design theory asserts that a supernatural intelligence intervened in the natural world to dictate the nature and ordering of all biological species, which do not evolve from lower-to higher-order beings. This article considers whether these intelligent design creationism proposals can survive constitutional scrutiny. The authors analyze the religious, philosophical, and scientific details of intelligent design theory, and assess these details in light of the constitutional doctrine developed by the Court in its previous creationism decisions. The Article discusses several factors that pose problems for intelligent design theory, including the absence of objective scientific support for intelligent design, evidence of strong links between intelligent design and religious doctrine, the use of intelligent design to limit the dissemination of scientific theories that are perceived as contradicting religious teachings, and the fact that the irreducible core of intelligent design theory is what the Court has called the “manifestly religious concept of a God or Supreme Being. Based on these details, the authors conclude that intelligent design theory cannot survive scrutiny under the constitutional framework used by the Court to invalidate earlier creationism mandates.