The purpose of information fusion is to support and improve decision making. However, theories of decision making differ significantly on their view of what a good decision actually is. Hence, depending on which decision making theory one (un)consciously adopts there are different requirements for information fusion as decision support Information fusion researchers and practitioners should therefore be more explicit about their assumptions regarding decision making by carefully describing their theoretical frameworks. To illustrate this point the 'theory of sensemaking' by Karl Weick is presented as one example of a decision making theory. Major differences between decision making assumptions in that theory and assumptions common in much information fusion research are highlighted. Implications and challenges for information fusion are discussed.