What is the main theme in the novel, Trader to the Stars?

Trader to the Stars opens with remarks by "Le Matelot" (The Sailor), who declares in part: "Because today we are sailing out among the stars, we are more akin to Europeans overrunning America or Greeks colonizing the Mediterranean littoral than to our ancestors of only a few generations ago. We, too, are discoverers, pioneers, traders, missionaries, composers of epic and saga."

This represents the principal theme of the book: that those who will travel in outer space will be frontiersmen. Some of these adventurers will be bandits, but others will be like Nicholas Van Rijn — daring people who use their wits to open up the universe to humanity and commerce.