Abstract: In this article it is argued that, far too often, conceptualisation of complex systems, development of user requirements and subsequent systems engineering activities do not produce the results expected. Attempts to more rigorously apply systems engineering practices fall short because the roles choice and decision making play are not well understood. Whilst systems engineers are taught to carefully weigh up options, the reality is that naturalistic decision-making, mental shortcuts or experience-based heuristics are routinely applied. So, systems architecting, which acknowledges the role of stakeholders and the use of heuristic-based decision making, is an important adjunct to conventional systems engineering, when it comes to development of complex systems. Conceptualisation of complex systems is more of an art than a science, and that art is affected in its application by organisational and cultural influences.