This article approaches common topics in the diachronic literature on modal categories from the perspective of adjectives. It thus expands on what has been found for the better studied category of modal auxiliaries as regards sources of modal meaning and pathways of change. Most importantly, it proposes two new pathways from premodal to (dynamic) modal meaning, one followed by essential and vital, and one followed by crucial and critical. It also shows that in the four cases the development of dynamic meaning depends on the emergence of two semantic properties, viz. relationality and potentiality. Finally, this study makes it clear that the mechanisms driving the various semantic changes are not new, but rather have proved useful in explaining a varied set of developments. For the final semantic extension of the adjectives from dynamic to deontic meaning, for instance, the process of subjectification (Traugott, Language 65: 31–55, 1989) will be invoked.