How Decorous of You

Carl Sagan's delivery of the Gettysburg Battle commemorative speech is such a rhetorical prowess.  The rhetorical skills employed in the speech are alone worth analyzing, but even more fascinating is Sagan's mastering of his decorum.

Sagan, in being there, being who he was, possesses all the three qualities of a persuasive ethos proposed in "Thank You for Arguing".

Without having heard a word from the speaker, the audience already has a certain predisposition for trusting Sagan, as he is a notable representative of science, the discipline of logic, evidence, questioning. People's beliefs regarding religion, politics, morals are all personal and often irrational, but when it comes to empirical evidence, few have the guts to disagree. People believe Sagan shares their values, because he believes in logic and proof, and those are unifying agents in an increasingly skeptical society. 

Most of the speech is just facts and figures about events which relate to the topic. For example, he opens the speech with, "Fifty-one thousand human beings were killed or wounded here..." These facts were undeniable, especially in a time without smart phones. Sagan's use of facts is a straightforward demonstration of his character and also a proof of his practical wisdom. He makes people believe he knows what he is talking about because, as a scientist, he values truth, therefore, beyond the fact that the topics covered are not of scientific nature, they must be true and relevant because that is the way Carl works. 

The mere presence of Sagan delivering the speech is the demonstration of the third quality: selflessness or disinterest. Sagan is not a politician, he is not in arms race for power, he is a simple academic with strong convictions. By delivering that speech it seems as if he is not doing it to achieve some personal interest. He has, in fact, not much to win by reprimanding the behavior of the two strongest nations in the world at the moment, and sadly a lot to lose. And yet, he does it anyway, because his true interest is the safety of humanity, not just Americans, but humans. 

All in all, Sagan's speech accounts for half of the persuasive techniques used. His mastering of decorum is what prepares the audience to listen attentively to what Sagan has to say. If the same speech was delivered by a republican presidential candidate (highly unlikely) the story would have been different.