Persuasion is a form of social influence. It is the process of guiding people toward the adoption of an idea, attitude, or action by rational and symbolic (though not always logical) means. It is strategy of problem-solving relying on "appeals" rather than strength.

Manipulation is taking persuasion to an extreme, where the one person or group benefits at the cost of the other.

Aristotle said that "Rhetoric is the art of discovering, in a particular case, the available means of persuasion."

Principles of persuasion

According to Robert Cialdini in his book on persuasion, he defined six "weapons of influence":

• Reciprocation - People tend to return a favor. Thus, the pervasiveness of free samples in marketing. In his conferences, he often uses the example of Ethiopia providing thousands of dollars in humanitarian aid to Mexico just after the 1985 earthquake, despite Ethiopia suffering from a crippling famine and civil war at the time. Ethiopia had been reciprocating for the diplomatic support Mexico provided when Italy invaded Ethiopia in 1937.

• Commitment and Consistency - If people commit, verbally or in writing, they are more likely to honor that commitment. Even if the original incentive or motivation is removed after they have already agreed, they will continue to honor the agreement. For example, in car sales, suddenly raising the price at the last moment works because the buyer has already decided to buy. See cognitive dissonance.
• Social Proof - People will do things that they see other people are doing. For example, in one experiment, one or more confederates would look up into the sky; bystanders would then look up into the sky to see what they were seeing. At one point this experiment aborted, as so many people were looking up that they stopped traffic. See conformity, and the Asch conformity experiments.
• Authority - People will tend to obey authority figures, even if they are asked to perform objectionable acts. Cialdini cites incidents, such as the Milgram experiments in the early 1960s and the My Lai massacre.
• Liking - People are easily persuaded by other people whom they like. Cialdini cites the marketing of Tupperware in what might now be called viral marketing. People were more likely to buy if they liked the person selling it to them. Some of the many biases favoring more attractive people are discussed. See physical attractiveness stereotype.
• Scarcity - Perceived scarcity will generate demand. For example, saying offers are available for a "limited time only" encourages sales.

Propaganda is also closely related to Persuasion. Its a concerted set of messages aimed at influencing the opinions or behavior of large numbers of people. Instead of impartially providing information, propaganda in its most basic sense presents information in order to influence its audience. The most effective propaganda is often completely truthful, but some propaganda presents facts selectively to encourage a particular synthesis, or gives loaded messages in order to produce an emotional rather than rational response to the information presented. The desired result is a change of the cognitive narrative of the subject in the target audience. The term 'propaganda' first appeared in 1622 when Pope Gregory XV established the Sacred Congregation for Propagating the Faith. Propaganda was then as now about convincing large numbers of people about the veracity of a given set of ideas. Propaganda is as old as people, politics and religion.