Both rhetorical theorists and attitude change theorists agree that characteristics of the source of persuasive communication can improve the persuasiveness of that message. Writers from both perspectives have approached this notion from two divergent perspectives. Isocrates was concerned with the speaker's prior reputation, which is quite similar to the extrinsic credibility studies that vary the characteristics of the source connected with the message. He also declared that prior reputation lent greater persuasiveness to all the words of the speech. Aristotle explicitly rejected the notion of ethos, focusing instead on variations in the language of the speech to create different impressions of the character of the speaker. This is quite similar to the extrinsic studies of credibility, which vary language, delivery, and rhetorical devices so as to alter the impression of the speaker and enhance effectiveness. Empirical studies have consistently supported the former conception, while the latter has been plagued by mixed results. Interestingly, one explanation for these results, drawn from the cognitive response approach, is quite close to Isocrates's explanation of ethos--that it lends persuasiveness to all the words of the speech. (HOD)