The document discusses the theoretical basis for effective public relations strategies. It outlines several key theories that PR practitioners can apply, including: 1. Relationship theories like systems theory and situational theory which examine an organization's relationships with external groups. 2. Theories of cognition and behavior such as social exchange theory and diffusion of innovation theory, which seek to understand how people think and make decisions. 3. Mass communication theories including uses and gratification theory and agenda-setting theory, which analyze how media influences society. Theories help PR practitioners develop persuasive strategies by understanding how people perceive information based on their own experiences and biases.