The Five Canons of Rhetoric

By the time Cicero comes about,  rhetoric would be divided into five major categories or canons:

1) inventio (invention) 
2) dispositio (arrangement)

3) elocutio (style)

4) memoria (memory)

5) pronuntiatio (delivery).

1)Inventio, Invention
This was the art of discovering a means for finding arguments on any topic.
2)Dispositio, Arrangement
This was the method of organizing an argument.
3)Elocutio, Style
 
Diction and the organization of phrases (tropes) became one's style. One's style was divided into three levels:  low (teaching), middle (persuading), and high (entertaining).
4)Memoria, Memory

 
The ability to use mnemonic devices to call forth and sustain an argument is the fourth canon.
5)Pronuntiatio, Delivery

 
 
Every speaker knows that without mastering this  canon, the other canons will not matter.  Demosthenes contended that this was the most important canon and is famous for replying  when asked what was the most important thing for a speaker to master: "Delivery. Delivery. Delivery."

In the eighteenth century, the Elocutionary Movement would popularize this canon.

In the sixteenth century, Peter Ramus would alter the importance of these canons and basically felt that rhetoric was merely style, memory and delivery.