Design and Planning professionals have long been influenced by the belief in physically and spatially deterministic power over people and the environment, a belief that their representations of space become space. As a result the goal of design often becomes "fixing" or directing behavior and culture instead of letting culture happen. This outlook often prevents designers from engaging critically with culture, through representational space and spatial practice, as a crucial, possibly the most crucial, aspect in the design process. Just as human cultures interact to constantly reproduce and co-produce hybrid cultures, the professional designer and those users and experiencers of design (at whatever scale) must interact to co-produce spaces and places of activity. Through a critique of the practice of placemaking, we highlight the need to differentiate between participation and co-production. Understanding participation as one element of the design process and the role of design at larger scales of co-productive processes can help designers have a better understanding of how spaces are produced, and the role of designers in the creation of spaces of potentiality. Agamben's writing on potentialities and Lefebvre's spatial triad offer a theoretical framework to investigate the ethical role of professional designers in society while taking a critical stance against the singular solutions of modernist urban transformation. Spaces of Potentiality are seen here as a designer's simultaneous withdrawal from rational problem solving and deterministic solutions, and an engagement with open source strategies for the co-production of urban space.