Herein, as general knowledge presupposes, the public is made up of a people in society. The word ‘public’ therefore is easily grasped. However, opinion “unlike fact, is unverifiable". That opinion is unverifiable, at least from the onset, with the mass public as its primary source is the foundation of the landmark book, Public Opinion by Walter Lippman. In part one of the book, Lippman wrote that every individual tends to have “pictures" of the world different from the real world. Furthermore, he wrote that human beings tend to formulate conclusions and make decisions based on these pictures or images.

Modern technology and statistical methods have been used by opinion pollsters to measure and track public opinion using random sampling of a given population. A majority response on a particular question is deemed to be a legitimate, weighty piece of public opinion. But while useful in getting answers questions that are simplistic – such as, “will you vote for Hillary Clinton if she runs for president in 2008?", opinion polls cannot gauge answers to complex issues. For example, issues facing the public such as the formulation of immigration policy for the new millennium or the question if business process outsourcing to developing countries will be good for the American economy cannot be directly answered by the public because a lot of facts and information are involved. The average citizen both in motivation and availability of information come up short in thoroughly understanding the issue or question at hand – even if they vaguely feel that these issues affect them somehow. Instead these issues necessitate the investigation of facts, discussion with the concerned parties and the crucial communication with the leaders in government who have been vested with executive powers to make official policy.

The complexity of issues that face crucial policy-making makes interest groups necessary. Citizens, who normally will not have the time or motivation on their own alone can be members of “voluntary societies" which will have the expertise or the motivation to gather data and peruse documents pertaining to certain issues. Interest groups and their ability to collate data and information form a third force or what Lippman calls “the wedge" between the mass public and the constantly changing, and increasingly complex environment.

Interest groups which are quite informal and formal organizations can include all sorts of groups and its permutations. But there are certain interest groups which have traditionally been viewed as either the savior or the carrier of public opinion in a democracy.

The press for example, especially in a democracy is viewed as bearing on its shoulders the responsibility of knowing the outside world mainly due to its comprehensive way of covering news and events. However news, mostly in a single story assignment is gathered from a limited scope of point of view. Adding up data or information hastily gathered from the field does not automatically translate to a clear way of making sense of public affairs or opinion. Even venerable media institutions which have gathered significant research over the years are constrained by economic factors with covering the world in its entirety. For example advertising concerns and political considerations may drive editors and publishers not to cover certain events resulting in bias reporting, whether intentional or not.

Like the media, social leaders and political leaders are also constrained by the fact that too much power considerations, both political and economic cannot possibly allow them to be the legitimate repository of public opinion.

While the concept of public opinion is considered too abstract or at best useful and tends to benefit only politicians and self--serving parties. This can be gleaned from the fact that the world has changed in its beliefs and practices due to public opinion, and due to the fundamental work of a small group or minority interest groups.

Before the start of the 20th century, emancipation of women, racial equality and environmental concerns on a universal level were virtually unheard of, until public opinion slowly drove them into fore.