15. Each moment of mental activity obtains the potential of transforming itself according to the range of the tenfold dharma-realm—the whole range between the lowest stage of ignorance and the highest of Buddha-wisdom. This means that mental activity, the medium of transformation must “embrace the three thousand worlds.” However, it is impossible to conceive of mental activity as a primordial mind causing things to arise, since mental activity cannot arise independently. According to the deconstructive function of emptiness, mental activity is not a disparate or independent entity temporally preceding all things existing; therefore, it cannot be regarded as the ultimate source of these things. On the contrary, mental activity is as much dependent on its existential habitat as this habitat relies on mental activity. However, since the existential habitat can be only transformed, if mental activity first transforms itself, mental activity has a soteriological priority. The subsequent discussion demonstrates that neither the ontological nor the temporal priority of mental activity can be held, while the soteriological priority must be emphasized; Zhanran’s (711–782) ambiguous phrase “one moment thought three thousand,” which deliberately lacks a verb, expresses this meaning. In Tiantai Buddhism, mental activity is considered as the medium of transformation due to this soteriological priority.