Over the last 40 years, many approaches to design have been put forward by various researchers, designers and engineers, both in academia and industry, on how design ought to and might be carried out. These proposals on design have tended towards what has come to be regarded as design philosophies, design models and design methods. The thesis of this paper is to discuss various aspects of generic research in design, within the above classifications in the light of the work that has been done in the last four decades. Discussions will focus on various definitions of design, design theory and methodology, the nature and variety of design problems, design classifications, philosophies, models, methods and systems.