The mathematical concept of symmetry, in its fullest sense, figured large in architectural history up to the early twentieth century. However, for the better part of a century, architecture and related disciplines have marginalized the consideration of symmetry in favour of a 'functionalist" conception of design. More recently, dramatic developments in mathematics, physics, biology, neuroscience, environmental psychology, and other fields have given new dynamism to the ancient topic of symmetry. These findings carry implications for architecture and other environmental design professions that have, until now, been poorly understood, where they have been considered at all. This paper examines the new findings and what they reveal about current design orthodoxy as well as shedding new light on historic precedents. It concludes that there is an urgent need for a reassessment, toward a new agenda of research and practice.