Final answer:
Polis uses the term "arteries of commerce" metaphorically to highlight the importance of channels and routes that sustain trade and economic movement, akin to how arteries in the body carry blood necessary for life.
Step-by-step explanation:
When Polis speaks about "arteries of commerce," he is using a metaphor where he likens the channels through which commerce flows to the arteries of the human body. Just as arteries are essential for carrying blood from the heart to various parts of the body, the "arteries of commerce" refer to critical routes and channels that facilitate the movement of goods, services, and trade from their sources to consumers and markets across geographies. This metaphor is powerful because it conveys the idea that these commercial pathways are vital for the economic health and vitality of a society, similar to how arteries are vital for the circulation of oxygenated blood and therefore the health of an organism.
The use of the word arteries in this metaphor greatly contributes to the power of Polis's rhetoric by emphasizing the importance of trade routes and channels. It evokes the sense that just as blockages in arteries can be life-threatening, obstructions in the paths of commerce could have dire consequences for the economic well-being of a nation or region. The metaphor thus effectively communicates the essential role of infrastructure and smooth transactions in the economic 'body.'