6 ideas
Simonides stepped out of a banquet moments before the roof collapsed, and the bodies were mangled beyond recognition. He named each corpse for the relatives by recalling where each guest had been reclining. Cicero presents this as the discovery that order of place is what makes memory retrievable.
Cicero advises choosing a set of places and forming images of the things to be remembered, then storing those images in the places. The order of the places preserves the order of the things, and the images stand for the things themselves. The places work like a wax tablet and the images like the letters written on it.
Cicero argues that impressions received through the eyes stick more firmly than those heard or reasoned about. So abstract or spoken material is best remembered once it is translated into visual form and given a location. Memory is therefore a matter of converting ideas into seen things.
Cicero recommends that memory images be vivid, sharp, and distinctive, so they can strike the mind and come back quickly. He gives this as a practical recommendation and does not develop a fuller theory of why unusual images work.
Crassus argues that nobody can speak well about a subject they do not understand, so the complete orator has to master philosophy, law, history, and the knowledge of human character. Rhetorical technique on its own gives polished emptiness. Eloquence comes from broad substantive knowledge joined to the ability to express it.
Oratory is divided into invention (finding arguments), arrangement (ordering them), style (clothing them in words), memory (retaining them), and delivery (voice and gesture). Each is a separate skill that can be trained on its own. Together they cover the whole path from thought to performance. Memory is treated as the treasury that holds all the other parts.