Design engages critical thinking at every stage of development. The initial concept requires both aprioristic analysis and empirical evicence (deductive and inductive logic), as well as a "creative leap" of the imagination into the proposal that is to be developed. In later stages, as the design process progresses through numerous iterations, decisions become increasingly refined by both research and testing of the design according to logically established parameters. Finally, when the design is complete, it is offered to a wider public for evaluation, which will take many forms and levels of rigor.