The basis for the transition to the new order of things must lie in the principle of the pure religion of reason, as a revelation permanently taking place within all human beings, and this basis, once grasped after mature reflection, will be carried into effect, inasmuch as it is to be a human work, through gradual reform. (6:122)

Kant says that adoption of his moral reason will happen gradually, and root itself into humans permanently. Once humans understand the principle behind "pure religion," and give the principle "mature reflection," they will begin to adopt it. Kant does not expect that his theories will take hold immediately. He understands that because this reform will be "a human work," it will necessarily happen through "gradual reform."