The practice of developing information systems with the support of information systems development methods is not new. A vast number of systems development methods have been suggested over the years in an attempt to solve the problems a development organisation might encounter. From early approaches like the Waterfall model to more modern monolithic methods such as the Rational Unified Process and the newest approaches exemplified in the Agile methods, the ambition has often been to find the silver bullet and the most effective ways to produce quality systems. Methods are prescriptive by nature as they suggest action and as such they represent rationale. Thus, one can speak of a method rationale as the dimension within methods that motivate their existence. Method rationale is understood as the goal and value rational relations between a method’s underlying philosophy and its proposed actions. During the methods’ evolution, the practice of systems development and the supporting systems development methods have been subjected to research from many perspectives. One possible way to understand the nature of the existing research is to separate it into two fields. The suggested fields have different strengths and weaknesses. The field of traditional research on information systems development (ISD) emphasise relevance in their studies but often overlook aspects of generalisation. The field of method engineering (ME) is highly formalistic and emphasise rigour but often miss aspects concerning relevance, such as the role methods play in peoples daily systems development efforts. In this dissertation, a polarisation of existing systems development method research is suggested in order to find a synthesis more capable of serving as a common ground for method research and for the understanding of the systems development method phenomenon. This is achieved through a proposed extension of the field of ME into the field of extended method engineering (EME). The foundation of the EME is found in the concept of method rationale and a method component concept design capable of carrying and expressing method rationale. The method component concept design is applied, evaluated, and re-designed in three different empirical settings in order to ascertain its practical potential and the benefits in explicating the dimension of method rationale.