This chapter arose from the keynote lecture to an international conference on Artificial Intelligence in Design. Rather than discussing ‘artificial intelligence’, it concentrates on the ‘natural intelligence’ of design. It addresses what we know about the natural intelligence of design ability, and the nature of design activity. The starting point was the observation that the ability to design is widespread amongst all people, but some people appear to be better designers than others. Quotations and comments from some acknowledged expert designers are used to reinforce general findings about the nature of design activity that have come from design research. The role of sketching in design is discussed in order to exemplify some of the complexity of designing. Finally, comments are made on the value and relevance of research into artificial intelligence in design. It suggests that one aim of research in AI in design should be to help inform understanding of the natural intelligence of design ability, to help us better to understand such natural intelligence, or human cognition.