The book, anchored in stimulating debates about the Enlightenment ideas of publicness, analyses historical changes in the core phenomena of publicness: possibilities, conditions and obstacles to developing a public sphere in which the public reflexively creates, articulates and expresses public opinion. It is focused on the historical transformation from “public use of reason” through the identification of “public opinion” in opinion polls to contemporary opinion mining, in which the Enlightenment idea of public expression of opinion has been displaced by the technology of extracting opinions. It heralds a new critical impetus in theory and research of publicness at a time when critical social thought is sharply criticising and even abandoning the notion of the public sphere, much like the notion of public opinion decades ago, due to its predominantly administrative use.