This essay explores the relationship between design, patterns, and form. It defines design as the act of making distinctions. Patterns capture proven solutions to recurring design problems within a given context. By applying patterns successively, form emerges as an adaptive response to design challenges. Each time a pattern is applied, it introduces distinctions at different levels: between problem and solution, form and context, or centers in general. The act of distinction creates a “boundary between two sides,” which Spencer Brown calls a “form.” The paper has three goals: 1. Develop the concept of patterns as distinctions by applying Spencer Brown’s calculus of form. 2. Define a practical language for reasoning about pattern sequences. 3. Offer an initial exploration of distinctions as a framework for understanding Alexander’s 15 properties. The audience for this paper includes anyone interested in pattern theory as well as patterns authors.