Walter Lippmann is an American journalist from the beginning of the 20th century. He is very influential with several American presidents, and a pioneer in the analysis of the training of consensus and public opinion. He recommends preparing information distributed to the media to ensure a uniform representation of social facts, ensure social cohesion, and avoid totalitarian excesses. This book emphasizing the fragility of public opinion in a democracy is a founding text for the study of the media. It is the precursor of many extensions: Overton window, Hallin’s spheres, manufacturing of consent, as well as for the passage of mass media to the Internet: ideological echo rooms, radicalization, and polarization of society.

A Seminal Book
Public Opinion is a book by Walter Lippmann, published in 1922. It is a criticism of the functioning of democracies following
the formation of division and irrational opinions on social facts, their influence on individual behavior, and their deleterious effect on social cohesion. It is a founding text in the study of the media, in political sciences, and in social psychology by its detailed description of the cognitive limitations of individuals in the face of their socio-political and cultural environment, a limitation which leads them to use an evolutionary catalog of stereotypes to interpret reality.
Pseudo-environment
The real environment is both too large, too complex, and too changing to be apprehended correctly. Each man builds a pseudo-environment which is a subjective and simplified image of reality. To a certain extent, each of these pseudo-environments is a fiction. People live in the same world, but they think, and they feel in different worlds.
Human behavior is part of the Pseudo-environment, but it gives rise to very real actions. The pseudo-environment is therefore a fiction, and its alignment within a population is of paramount importance to allow coherent action. The work presents the influence of the media on this stereotypical perceptual framework.

He could not conduct his tax reforms deemed unacceptable in 1787 by the assembly of the notables which he had nevertheless sorted on the aspect. Opinion was too divided.

The general estates were summoned by french Minister Necker who nominated more Third Estate representatives to overcome the privileges of the notables and obtain the means to resolve the crisis.
Journalism and truth
A fact cannot be presented exactly. The description of an event requires composition, arrangement, and interpretation. Those who are most aware of the facts concerning the environment build a pseudo-environment they communicate to the public, which is aligned with their stereotypes and their subjective reading of reality. The media as information transmission vehicles are particularly vulnerable to manipulation.
The media are not the only ones responsible for such manipulation. Responsibility is also responsible for certain members of the public who consume news with little intellectual commitment. With the following consequences:
The consumer public buys information from the media that allows him to understand the world. The public is selective and will pay as little as possible for a representation to which he intends to be faithful and coherent of reality. "While for a dollar, you can't even get a handful of candies, for a dollar or less, people hope for an exact representation of reality. "
Newspapers are above all companies that must sell their product and strive to maintain a professional and objective image of their work. Only the news from official sources is presented because the rest is not confirmed and could be accused of canard. Unofficial or private news is unavailable.
The news report changes. These signals are the deliberate consequence of the editorial policy of a media. Journalism shapes public opinion.
Lippmann concludes poetically: "To traverse the world, men must have maps of the world. Their persistent difficulty is to secure maps on which their own need, or someone else's need, has not sketched in the coast of Bohemia.".
Manufacture of consent
When deployed in the general interest, the manufacture of consent is useful and necessary for social cohesion. In many cases, the common interest of the public is not obvious except after a careful analysis of the data. This analysis is a critical exercise that is out of reach for most people, either because it does not interest them, or because they are incapable of it. For this reason, most must have the information summarized and presented by the best-informed persons, after which they can act accordingly.
The political elite are unable to understand the invisible and complex environment that determines the affairs of a modern state. Lippmann proposes that a professional class of specialists collects and analyzes data, and presents their conclusions to the decision-makers of a company. They in turn use the art of persuasion to inform the public of the circumstances and the decisions which affect them.
Public opinion suggests that the power of propaganda and specialized knowledge required for political choices in the public interest have made traditional democracy impossible. A question linked to the manufacture of consent and explored in 1997 by Timur Kuran is the falsification of preferences, whereby a silent majority avoids confrontation with an organized minority so that the Overton window is more extreme than the median opinion. This is another demonstration of the power of special interests in collective action issues.
Reception and influences
Walter Lippmann advised American presidents in the 1930s. It aimed for the liberal or libertarian state to make a cohesive consensus and societal vision to combat totalitarian ideologies which have very effective propaganda on the masses, and flourish in the soil of social division (be it communism based on the opposition of the poor and the rich, or the fascists and their identity and nationalist opposition).
Lippmann's work appeared in 1922, 4 years after the end of the First World War and 9 years after the creation of income tax. He was therefore going to encourage the use of considerable funds raised by the federal administration to develop specialized statistical offices. We think of the Nber (1920), FTC (1914), FDA (1906), BLS (1884). The high amount and the sustainability of federal tax would seal the superiority of the federal policy over the policy of the Union states.
The concept of the manufacture of consent has been taken up and developed by other authors:
Overton's window assumes that political discourse is restricted by a window of public opinion. There is a gradation of the unthinkable to the radical, from radical to reasonable, from reasonable to popular, and the politician can only propose policies in a limited field.
Hallin's spheres describe a categorization by the media of opinions between a sphere of consensus, a legitimate controversy sphere, and a sphere of deviant opinion. Regardless of the merit of an opinion, a journalist will therefore defend what is part of the consensus of his audience, organize debates in the legitimate sphere of controversy, and will censor the opinions deemed as deviant. For example, the abolition of rent control in France, or the implementation of universal health insurance in the United States are deviant ideas outside the field of acceptable political debate even if these measures are part of the consensus in other countries.
Socialist Noam Chomsky wrote a book inspired by the theories of the neoliberal Walter Lippmann: The Manufacture of Consent explains how the media in the United States were able to support disastrous military interventions abroad and censor political discourse concerning universal health insurance.
More recent studies show amplifying, radicalization, and echo chamber effects on the Internet, and the polarization of society. Hallin's spheres would begin to separate.