This thesis deals with the term 'context' and the aim has been to reason about the term in order to see whether it is possible to reach a satisfactory understanding of the concept. But the thesis is also a journey into human reasoning and conveys a certain view of human cognition. It aims to synthesise results of studies within psychology, cognitive science, anthropology, and human-computer interaction. My understanding is that context is not something we are a part of, but rather something we create mentally in relation a specific goal. Determination of something ambiguous thus comes from top-down processes related to a goal. I believe context has been wrongly interpreted in HCI as that which a user is situated in and which a product is being used in. I suggest instead a separation between the user environment and the user context.