Sentence:  This may signify much; among other things that the courtesan is creeping into social favor—even that a new code of morals is now <WSD>abuilding</WSD>, in which she will be the grand exemplar. 
Meaning of the word marked with <WSD> tags:  Developing or arising, as a trend or an idea. (First attested in the mid 16th century.)<ref name=SOED/>