Sui generis

“Because we have to use numbers so much we tend to think of every process as if it must be like the numeral series, where every step, to all eternity, is the same kind of step as the one before. ... There are progressions in which the last step is sui generis—incommensurable with the others—and in which to go the whole way is to undo all the labour of your previous journey.”

“According to the extent to which a spirit is sui generis, the limits of what is permitted—that is, beneficial to him—become more and more narrow.”