Isadora Duncan's writing, "The Dance of the Future" was originally published as an article by Theater Arts Books in 1928 before being adapted into a series of works entitled "Dance as a theatre art : source readings in dance history from 1581 to the present" in 1992. This is noted at the bottom of the aforementioned book's page. By compiling this and other works, they intended to create a more linear history of aesthetic dance. However, the Duncan piece was originally presented as a speech in Berlin in 1903.
This source was clearly conceived to detail Duncan's (the creator's) ideas on how dance-like movement should be practiced and how she will accomplish that. Duncan's writing style is so certain, almost philosophical. Her allusion to oceans and birds and the ancient Greeks places her argument deep within history, and yet, her argument is an opinion still. Likely, she was trying to convince a broad audience of woman (white, certainly) who were looking to partake in aesthetic movement, or perhaps were otherwise engaged in traditional modes of dance. Duncan begins by berating ballet in particular, claiming the practice was deforming to the body and unnatural. She then goes on to humbly yet strongly present her idea for the very unbound "dance of the future." She even goes so far as to call the new dance "the ideal form of woman" and a "high religion art." This powerful language seeks to entice an audience of progressive and curious women. While the argument is persuasive, she does not describe any of the actual movements that would qualify as "the dance of the future." This could be because there is no set definition, but by not drawing a clear line between her idea and ballet, for example, the argument is slightly confusing.
Prior to this writing, the early 20th century was experiencing a growing fascination with spiritualism and free movement. This could very well be due to the explosion of immigration in the 1900s and the rise in feminism. In particular, yoga and nautch dancing was growing in popularity thanks to presentations at the World Fair and similar events. Thus, the acceptance of Duncan's ideas is better understood when considering this context.