Effective Inquiry for Innovative Engineering Design presents empirical evidence for this claim. It demonstrates a unique attribute of design thinking by identifying and characterizing a class of questions called "Generative Design Questions". These questions are frequently asked by designers in dialog. Their use constitutes a fundamental cognitive mechanism in design thinking. Their discovery stems from another finding of the work: a conceptual duality between questions and decisions that is engraved deep within the design process. This duality challenges a view that treats designing as decision making. Decisions form the tip of the iceberg; Questions keep it afloat: Can an effective decision making process be performed without having high