Design has evolved from a craft into an academic discipline, but it still falls short on defining its own science. I review previous approaches to Design Science and conclude that the subject– object dualism is the one of the main obstacles. I then apply the Metaphysics of Quality to overcome the dualism and propose Quality as the phenomenon of Design Science. Next, I propose to utilize the analysis of interaction effects as a mean to investigate Quality. Last, I recommend steps we can take to mature this new Design Science and strategies how we can gain the acknowledgement of the other sciences. Categories and Subject Descriptors H.5.m Miscellaneous General Terms Design, Theory Keywords Metaphysics of Quality, Design, Theory, Science, Interaction Effect