The first part of this chapter concentrates on the nature of design ability, drawing upon a variety of studies and investigations into design activity and designer behaviour. From a review of these studies, design ability is summarised as comprising abilities of resolving ill-defined problems, adopting solution-focussed cognitive strategies, employing abductive or appositional thinking and using non-verbal modelling media. These abilities are highly developed in skilled designers, but they are also possessed to some degree by everyone. A case is proposed for design ability to be seen as a fundamental form of human intelligence. The second part of the chapter argues that understanding the nature of design ability is necessary in order to enable design educators to nurture its development in their students. The nurture of this ability through design education is discussed with particular reference to the problem of providing design education through the distance-learning media of the Open University. ‘Open-ness’ is emphasised as a key principle for modern design education.