This project develops a new theory of how persuasive communications influence social attitudes. The new theory challenges many prevailing views of persuasion and attitude change. Most contemporary theories of persuasion identify two distinct ways in which persuasive influence occurs: (1) through the persuasive message itself, based on the force of the arguments it contains, or (2) through features external to the message, such as the communicator's status or prestige, or the number of different people supporting a certain position. These theories also suggest that persuasion accomplished through message arguments is more robust, long-lasting, and resistant to subsequent change than is persuasion achieved through external features. The current project introduces a new theory in which the two seemingly different modes of persuasion actually constitute special cases of the same underlying process. These cases differ in the contents of evidence by which one may be persuaded, but not in the way those contents function to change people's attitudes. Seven experimental studies test this novel theory of persuasion. The experiments are based on an analysis showing that prior experiments have confounded general informational features (such as length/complexity, order of presentation, and relevance) with whether the information is contained inside (vs. outside) the message itself. By controlling for these confounds, it should be possible to demonstrate the functional equivalence for persuasion of these different types of information. A significant implication of the new theory is that robust, long-lasting, and resistant persuasion may be accomplished on the basis of external cues. This analysis has fundamental implications for a large number of areas in which persuasion plays a role, such as education, therapy, health and environmental-protection advocacy.