Design rationale is a term used to focus on the underlying reasoning behind a design intention.

It concerns the basic structure of thought that brought the design into being. Sometimes referred to as ‘intellectual underpinning’, the design rationale aims to distinguish between the intuitive and the cerebral, and to represent the bedrock on which concepts are structured.

However, it must be added that while it is difficult to apply logic to an instinctive approach, the ultimate response may represent a balance between the two.

‘Pet idea’ is a common type of design rationale that typically needs to be aired early on so it can be discarded or be allowed to evolve into a legitimate design rationale. When a developed intention is declared in a ‘mission statement’ or presented as a mini-manifesto and, hopefully, made visible in the proposed design, the design rationale flies in the face of whimsical or willy-nilly design attitudes and challenges a ‘prima donna’ approach.