Where causation is a set of behavioural principles aimed at controlling the agents future through prediction, effectuation focuses on achieving control without relying on predictions. This research explores how an organization can use a mix of causal and effectual principles, and what the drivers of such behaviour are. In doing this, a basis is created for using the principles of causation and effectuation as an analytical framework. To explore the interplay between causation and effectuation, a theory generating single case study was conducted at Enviu, a Dutch NGO which aims to add environmental and social value by scouting, generating and implementing sustainable ideas. Two major projects within the organization were investigated using the grounded theory method. Data from documentation, interviews and observation was grouped into constructs, after which links between these contructs were developed, forming propositions for new theory. Enviu is characterized by a hybrid behaviour, incorporating heavy use of partnering, research and working on basis of affordable loss, where opportunities are pursued only if failure can be afforded. It also showed to be quite risk-averse. To explain this behaviour, a driver model was synthesized from literature, and additional drivers were developed. The main contributions of this research are two new drivers for behaviour. First, it was shown that financial partners not directly involved with the project operations stimulate the use of causal principles through their need for measurable control mechanisms. Second, low available means result in a fragile organization, stimulating the use of risk reducing principles originating in both causation and effectuation. Noteworthy are the increased use of partnering (to increase the available means), affordable loss and prediction, as well as the decreased use of experimentation. Together, these drivers explain Enviu's behaviour to a very large extent. The drivers emerging from literature - uncertainty, efficacy of the organization, entrepreneurial expertise of the individual and self-efficacy of the individual - played a lesser role in determing the behaviour. The findings of this research were translated into recommendations for Enviu. These recommendations discuss how Enviu should chose, attract and maintain relationships with partners, how Enviu can improve its performance by experimenting at low cost and how Enviu should react in case of a situation of increased means. This is a proof-of-concept of using the causal and effectual principles as an analytical framework, from which meaningful advice can be derived.