This refers to any revolutionary change in the fundamental intellectual framework that has traditionally been adopted by practitioners of a subject. The idea was proposed by American philosopher Thomas Kuhn in The Structure of Scientific Revolutions . Kuhn believed that the central ideas of a discipline generally do not change within a short span of time or because the current practitioners readily change their minds when they are introduced to new and better ideas. Instead, he argued, paradigm shifts happen when people of the older generation die and are replaced by younger people who are more receptive to newer ideas.