After examining which laws are related to the nature of each government, we must see which ones are related to its principle.
The difference  between the nature of the government and its principle is that its nature is what makes it what it is, and its principle is what makes it work. One is its particular structure, and the other the human passions that put it in motion.
Now laws should be not less related to the principle of each government than to its nature. We must therefore try to identify that principle. That is what I am setting about to do in this book.