Definition
Intelligent design, often abbreviated ID, is the claim that certain features of the universe and of living things are best explained by an intelligent cause rather than by an undirected process such as natural selection. Proponents argue that some biological structures display a kind of complexity that, in their view, points to a designing intelligence.
ID is a modern descendant of the classical argument from design. Its advocates generally present it as a scientific inference and do not, within the argument itself, name the designer, though critics note that the wider movement is closely associated with religious objections to evolutionary biology.
Why it matters
How it works
ID proponents look for features they describe as "specified" or "irreducibly" complex and argue that an unguided process is too improbable to produce them, leaving design as the better explanation. The bacterial flagellum and the blood-clotting cascade are among the most cited examples.
The standard scientific response is that natural selection builds complex systems gradually, with parts often co-opted from earlier functions — so a system can be assembled stepwise even if removing a part now breaks it. Dawkins develops this reply in detail, treating apparent design as the expected outcome of cumulative selection. A 2005 United States court case, examining ID in a school setting, concluded that it was not science. Supporters of ID continue to dispute these assessments.