 The fusion method provides a simple yet powerful strategy for adding a further aspect to an existing modal system by using another already existing system dealing with this further aspect independently. Indeed, the discussed example can be seen as adding a temporal aspect to the standard study of the properties of knowledge. Besides the traditional epistemic questions (e.g., whether knowledge should be positively/negatively introspective), one can also discuss not only whether knowledge should change, but also the different ways in which it might so.