Context Methods and processes, along with the tools to support them, are at the heart of software engineering as a discipline. However, as we all know, that often the use of the same method neither impacts software projects in a comparable manner nor the software they result in. What is lacking is an understanding of how methods affect software development. Objective The article develops a set of concepts based on the practice-concept in philosophy of sociology as a base to describe software development as social practice, and develop an understanding of methods and their application that explains the heterogeneity in the outcome. Practice here is not understood as opposed to theory, but as a commonly agreed upon way of acting that is acknowledged by the team. Method The article applies concepts from philosophy of sociology and social theory to describe software development and develops the concepts of method and method usage. The results and steps in the philosophical argumentation are exemplified using published empirical research. Results The article develops a conceptual base for understanding software development as social and epistemic practices, and defines methods as practice patterns that need to be related to, and integrated in, an existing development practice. The application of a method is conceptualized as a development of practice. This practice is in certain aspects aligned with the description of the method, but a method always under-defines practice. The implication for research, industrial software development and teaching are indicated. Conclusion The theoretical/philosophical concepts allow the explaining of heterogeneity in application of software engineering methods in line with empirical research results.