It is difficult to over-estimate Cicero's importance to the history of rhetoric even if it's relatively easy to overestimate his reliability as a historical source. He was a prolific scholar. According to the Wiki article, "he wrote more than three-quarters of surviving Latin literature from the period of his adult life, and it has been said that subsequent prose was either a reaction against or a return to his style, not only in Latin but in European languages up to the 19th century." (link). Ponder that assertion for a moment. Seventy-five percent of what we know about Latin literature is directly attributed to Cicero.
Part of what makes him so helpful to people interested in this time is that in addition to his many books and published speeches and the hundreds of letters detailing all aspects of his personal and political life, We owe the survival of Cicero's work in large part to Tiro, Cicero's slave/secretary/scribe, who outlived Cicero by 60 years and devoted his life as a freeman after Cicero to his own writing as well as publishing Cicero's work. Tiro is also thought to have invented shorthand. (link) Cicero practically invented PR. The no doubt disproportionate size of the work Cicero left relative to everything else written at the time and his practice of revising and publishing speeches he gave and in some cases, Lucius Verres, for example, he never actually gave, left posterity with the impression that Cicero's truths were the truth, that his perspective was not a perspective but rather reality. This is of course bad thinking. Cicero was an advocate for his own cause always. And those who opposed him left nothing or little to help us understand their point of view. Mary Beard, in Confronting the Classics (chapters 8 and 9 in particular) does an excellent job of advocating for the defense and in the process makes it abundantly clear that we ought not trust Cicero to speak for his time.
The reason Cicero was so successful in painting the future's impressions of his time may come down to the fact that his speeches became part of rhetorical curriculum and thus generations of young orators learned both theory and practice directly from his writing. Those who learned Latin with no oratorical aspirations were also overly influenced by Cicero. As Beard points out, "Since the eighteenth century the first paragraphs of In Catilinam 1 have been regularly used as the trial text for specimens of typesetting (and now of web pages) p 85. The origin of Lorem Ipsum is itself disputed. The Internet thinks it comes from De Finibus and that it is garbled but ultimately attributable to Cicero see this and also this.
Because I don't read Latin and I am far too humble to take issue with a Classist's knowledge of Cicero, I'm moving on having merely noted that even garbled Cicero is still being echoed everywhere print culture and its descendants live.
Cicero had a front-row seat as the Roman Republic transitioned into the Roman Empire; he tried valiantly (if we are to believe him) to save the Republic, but he did not have a hand in Caesar's assassination. After Caesar's death, Cicero and Mark Antony vied for political dominance. Cicero wrote and delivered a series of speeches denouncing Mark Antony, which he called the Philippics after Demosthenes's attacks on Phillip of Macedon at the twilight of Athens' preeminence three centuries before. Eloquent as Cicero was, Antony survived the verbal assault. When Antony joined forces with Octavian (Caesar's nephew and ultimately the first emperor of Rome), Cicero found his name among those proscribed, that is on the list of people whose head (literally) Octavian and Anthony would pay for. Tradition has it that when the soldiers caught up with him, Cicero said, "There is nothing proper about what you are doing, soldier, but do try to kill me properly." The topic of different gramatical forms. He then bared his neck and accepted his fate with dignity and grace (a chriea, for certain. We have nothing but testamentary evidence to support the truth of how it happened. And I have a hard time imagining a soldier in search of bloody gold would paint such a sympathetic picture.) No doubt, however, many people saw his head and hands displayed in the Forum. As Wiki relates, "According to Cassius Dio (in a story often mistakenly attributed to Plutarch),[109] Antony's wife Fulvia took Cicero's head, pulled out his tongue, and jabbed it repeatedly with her hairpin in final revenge against Cicero's power of speech.[110] " State craft as stage craft at its most vivid. But also quite possibly just another chreis mistaken for a historical moment. The rhetoric of history is the history of rhetoric.
Among his many works -- speeches, letters, poems, philosophical tracts -- are five books on rhetoric:
Although he was profoundly important to rhetoric, he was not an innovator. Most of what he tells us we know from other sources, though of course knowing his opinions about rhetoric and orators of his time is uniquely important. Of the five books on rhetoric, De Orator and De Inventione are the most frequently read today.
De Inventione, being a handbook of rhetoric and basically school notes, which Cicero claims he never intended to make public and which he wrote while still a teenager, is the most practical of the five. Below I have paraphrased what he had to say there about arrangement. You might see what's there as an ancient and more august ancestor to the Five Paragraph Essay of today.
It's quite likely that De Inventione became a standard rhetorical handbook and was read by many generations of would-be Ciceros. Below is my paraphrase of Cicero's advice about how to arrange a speech.
The goal is to say what happened or will happen in a memorable and pointed fashion, so that your audience believes what you say and is moved or unmoved to the degree your case requires. Be brief, concise, and clear. Have the people in your narrative speak the way your audience expects such people to speak, rely on the habits of ordinary people and the beliefs of your audience to guide what you say (verisimilitude, realism). Use chronological order for events, logical order or accepted hierarchy for ideas. If you have to use an uncommon structure, explain what it is in advance. Avoid obscurity (saying too little) and repetition. Do not narrate base or disgusting events--Arist: use circumlocution if the name is base, use the name if the thing is base.
Here you state the issue (from stasis theory). What question must be answered and what two contradictory answers must the audience choose between. Here you may also want to account for the difference of opinion by explaining the motivation of those who oppose you, or by promising information which those who oppose you do not have. One form of partition is to indicate what is agreed to and what is disputed. Another is to divide the issue into its elements, laying out each claim which must be proven. Then you simply handle each claim in the order in which you just set them out (see page 69 for examples). Whatever arrangement you decide on, be complete, precise, and brief.
Those "parts of an oration which by marshaling arguments lends credit, authority, and support to our case" (69). Consider the topics relevant to characters and actions: manner if life, education, professions, home life, fortune, reputation, public office, habits, arts, knowledge, feelings, interests, motives, goals. The topics for actions: place, time, manner, occasion, facilities, opportunity, proximity, duration, order of events, manner of action, results, similar instances, contrastive examples, frequency, rarity, honor, advantage. Consider also arguments from probabilities based on maxims, analogies, signs, previous judgments, religious sanctions, common practices. When you construct an enthymeme out of this material, consider whether the premise requires proof or can be asserted without additional proof (see epichireme 101-12)
"It uses the same sources of invention that confirmation does, because any proposition can be attacked by the same methods of reasoning by which it can be supported" (123). Look to the opponent's enthymemes. Deny the link between the premise and the conclusion. Deny the assumption on which the enthymeme is based. Deny the conclusion. Supply counter examples. Remember that evidence almost always cuts both ways. What seems like obvious proof to you can be swiftly turned against you.
Fifteen topics of indignation--ways to amplify the enormity of the situation. Not all of these will always be applicable. Some of them are not carefully thought out. Make of these what you will.
Sixteen topics for evoking pity. Again, proceed with caution. If you get caught trying to amplify the emotions involved, you will lose all credibility and you will achieve the reverse effect.
But remember: "Nothing dries more quickly than tears" (163).