This paper examines design from a ‘knowledge integration’ research perspective, a field which enables us to explore the nature and scope of the knowledge involved in design. The integration of technically rational and human-centered knowledge is central to design (‘integration of design’). However, design is also a core knowledge generating process (‘integration by design’) which, although sometimes overlooked, elevates design from a functional task to a strategic activity of the firm. The paper explores the meaning and implications of the scope of design knowledge, highlighting the interplay between technically rational and human-centered aspects, including symbolism, meaning and aesthetics. By examining how the nature and scope of the design knowledge being integrated influences the design process we deepen our understanding of the complexities of design and design practice.