I was a little baffled last week when Dave was explaining common places, so I made sure to mark that section in Book 2 for myself. I was originally picturing the common place as the location of a space that everyone could understand. Here in America land we could call the idea of "freedom" a common place (the way I was picturing it in my head); a topic that everyone has some feeling on, some endoxa, some sense of knowing. Then Dave said... Ummm, No, that a common place are "a relational concept that is given content." Okays.
Now that I have read through some of this though I think that I understand. These common places, the Topoi, are the turning point of the argument, or the movement of the argument, or the key stone, or the load stone of the argument. An author's action that is weak... Thinking about it in the place way I am imagining walking through a maze and there is a point where a rhetorician is asking you to go with them down this dark corridor, and if you go, you loose (Would you agree that...?). Or the architecture of an argument, where there is a move as they are building it and if we can take out that move the whole building comes crashing down. Places to pick at, or to employ.
Demonstrating, using grammar to be tricky, correlating, more or less, time, turning the argument against yourself, definition, synonyms, devision, induction, judgment of like or opposite... it goes on and on. You can even watch for a religious argument and get them on that: "What kind of motion of the soul? For it is this or that" (197). I think that I am starting to understand where these might come in handy though...