The central idea that informs Macaulay's book is aptly expressed in a passage he quotes from Sapir (1929:214):

Language is primarily a cultural or social product and must be understood as such ... It is peculiarly important that linguists, who are often accused, and accused justly, of failure to look beyond the pretty patterns of their subject-matter, should become aware of what their science may mean for the interpretation of human conduct in general. (138)