Monopolies of knowledge arise when the ruling class maintains political power through control of key communications technologies. The Canadian economic historian Harold Innis developed the concept of monopolies of knowledge in his later writings on communications theories.

An example is given of ancient Egypt, where a complex writing system conferred a monopoly of knowledge on literate priests and scribes. Mastering the art of writing and reading required long periods of apprenticeship and instruction, confining knowledge to this powerful class. It is suggested that monopolies of knowledge gradually suppress new ways of thinking. Entrenched hierarchies become increasingly rigid and out of touch with social realities. Challenges to elite power are often likely to arise on the margins of society. The arts, for example, are often seen as a means of escape from the sterility of conformist thought.

In his later writings, Innis argued that industrialization and mass media had led to the mechanization of a culture in which more personal forms of oral communication were radically devalued. "Reading is quicker than listening," Innis wrote in 1948. "The printing press and the radio address the world instead of the individual."

We can look at the Internet as being a factor in creating knowledge monopolies. Those who have the skills to use the technology have the power to choose what information is communicated. The significance of the Internet in the creation of these monopolies, in more recent years, has been somewhat diminished due to increased knowledge and awareness of how to use the technology. At the same time, the ever-increasing complexity of digital technologies strengthens monopolies of knowledge, according to the New York Times:

[T]he Pentagon has commissioned military contractors to develop a highly classified replica of the Internet of the future. The goal is to simulate what it would take for adversaries to shut down the country’s power stations, telecommunications and aviation systems, or freeze the financial markets — in an effort to build better defenses against such attacks, as well as a new generation of online weapons.

Wherever new media arise, so too do monopolies of knowledge concerning how to use the technologies to reinforce the power and control of elite groups.

When discussing the monopolies of knowledge, Innis focuses much of his concern on the United States, where he feared that mass-circulation newspapers and magazines along with privately owned broadcasting networks had undermined independent thought and local cultures and rendered audiences passive in the face of what he calls the "vast monopolies of communication". James W. Carey notes that Innis worried about the centralized control of information and entertainment by advertising-driven media. "The very existence of a commodity such as 'information' and an institution called 'media' make each other necessary," Carey writes. "More people spend more time dependent on the journalist, the publisher, and the program director. Every week they wait for Time [magazine]."

In order to fashion his concept of monopolies of knowledge, Innis drew on several fields of study, including economics, history, communications and technology.