 It becomes immediately clear that no system involving a single modality can deal with this situation, as the description includes not only two agents (so, at least two modalities would be required), but also two different concepts: beliefs and assumptions. Thus, to make formal sense of this situation, one requires a system that allows us to deal not only with different attitudes, but also with the complex relationship between them. To make formal sense of this (and other similar) situation(s), one requires a multi-modal system.