Final answer:
The Elaboration Likelihood Model is the most relevant theory for a speaker developing a persuasive speech, considering the source credibility, message subtlety, and timing. Ethos, logos, pathos, and kairos are key persuasive strategies derived from ancient Greek rhetoric, crucial in situations requiring the sway of public opinion or legal disputes.
Step-by-step explanation:
The communication theory most relevant to a speaker developing a persuasive speech can be attributed to the Elaboration Likelihood Model of persuasion. This model, introduced by Petty & Cacioppo in 1986, suggests that the persuasiveness of a message is affected by features of the source, message content, and audience characteristics, influenced by two main routes: the central and the peripheral route. Key aspects like the speaker's credibility and physical attractiveness, message subtlety, sidedness, and timing impact the effectiveness of persuasion.
In addition, the framework of ethos, logos, pathos, and kairos—originating from ancient Greek rhetoric—serves as a foundational basis in Western civilization for developing a persuasive strategy. The kairos, or the aspect of timing, plays a critical role as it determines the appropriateness of the appeal in relation to the timing of the communication.
When developing persuasive communication, especially within legal professions or situations requiring the sway of public opinion, an understanding of these rhetorical strategies is essential for effectively influencing an audience's attitudes and behaviors. The application of these communication theories can be seen in various advocacy efforts, from op-eds to public speeches, and in the legal world, from courtroom arguments to negotiation tactics.