Final answer:
The common theme of the Preamble to the Constitution and the Declaration of Independence is that a government's primary responsibility is to protect man's natural rights.
Step-by-step explanation:
The theme that best represents both the Preamble to the United States Constitution and the Declaration of Independence is that a government's sole responsibility should be the protection of man's natural rights. This theme is grounded in the Enlightenment principles and the theories of English political philosopher John Locke, who argued that people have natural rights to life, liberty, and property, and that governments are created to protect these rights. If a government fails to protect these rights, the people have the right to alter or abolish that government—a revolutionary idea that underpins both the Declaration of Independence and the Constitution's Preamble.