The dominant view of design in information systems and software engineering, the Rational Design Paradigm, views software development as a methodical, plan-centered, approximately rational process of optimizing a design candidate for known constraints and objectives. This paper synthesizes an Alternative Design Paradigm, which views software development as an amethodical, improvisational, emotional process of simultaneously framing the problem and building artifacts to address it. These conflicting paradigms are manifestations of a deeper philosophical conflict between rationalism and empiricism. The paper clarifies the nature, components and assumptions of each paradigm and explores the implications of the paradigmatic conflict for research, practice and education.