The focus of this study is scenario planning, an approach that is widely used by businesses, policy makers and NGOs to explore the future in a systematic manner. Despite the extensive use of scenario planning and more than 50 years of scholarship, the field is still in a preparadigmatic state and scenario planning lacks a theoretical and methodological foundation. This research aims to address this gap by developing a foundation of principles and theory of scenario planning. Focusing on the intuitive logics tradition, the researcher examined the practice of scenario planning, i.e. what scenario planning experts do when exploring the future. The central research question that guides this thesis is: What practices do intuitive logics scenario planning experts enact when exploring the future? The researcher conducted multiple case studies and data were collected in very extensive and in-dept interviews with many of the world leading experts on scenario planning from Royal Dutch Shell and Global Business Network (GBN). This research found that scenario planning experts seek to understand the clients of the scenario planning project, establish the scenario focus, examine the external environment, develop scenario sets, challenge the assumptions and beliefs of the clients, and catalyse conversation and dialogue. The findings of this study are novel and challenge several well-established ideas in the literature. Remarkably, the findings of this study suggest that the term intuitive logics is not an appropriate name for the field and that the GBN 2x2 matrix method is not the ‘standard’ or ‘dominant’ approach. Most importantly, the practice of scenario planning was found to be surprisingly similar among the participants of this study, however, the way it is enacted can also be vastly different among experts and projects. This is important work that matters, especially in our turbulent times. The findings of this study inform and support the practice of scenario planning, contribute credibility and legitimacy to the field, as well as provide a foundation for further field building.