Resistance is Futile; Formal Linguistic Observations on Design Patterns Peter van Emde Boas Abstract: Inspection of the current literature on Design Patterns shows that the Prime Directive for this community is Pragmatics. It hardly matters what patterns are, or how Patterns are represented formally or syntactically. What does matter is their role in enhancing the reuse of good solutions to recurring problems. In this article I want to show that minimal assumptions about the pragmatic use of Patterns suffice to show that Design Patterns form just another formal language, which can be shown to be at least Recursively enumerable. Whether the language is Recursive depends on further conditions on the actual relation which is assumed to hold between a pattern and its possible invocations. There are no a priori reasons enforcing that this should be an easily decidable relation; quite to the contrary: a little amount of linguistic expressivity suffices for showing that this relation is likely to be complex. Without restrictions on the linguistic tools allowed for expressing design patterns this relation will become undecidable. For NonÂDesign Patterns which leave no visible trace in the designs constructed using them, the argument doesn't apply.