Final answer:
The main purpose of the Declaration of Independence by Thomas Jefferson was to declare independence from British rule and establish the colonies' rights to life, liberty, and the pursuit of happiness, alongside the right to form a new government reflective of the peoples' will.
Step-by-step explanation:
The author's main purpose in the Declaration of Independence by Thomas Jefferson was to formally announce and justify the American colonies' separation from British rule. Influenced by Enlightenment philosophers like John Locke, Jefferson emphasized that people have inalienable rights to life, liberty, and the pursuit of happiness and that governments are established to protect these rights. The Declaration not only listed grievances against the British king but also established the foundation for a new kind of government based on the consent of the governed. It ultimately helped to define the democratic principles upon which the United States was founded and set a precedent for the protection of civil liberties.
By declaring independence, the document serves as a cornerstone for American political thought, emphasizing that when a government becomes destructive to these ends, it is the people's right to alter or abolish it. The Declaration of Independence is a testament to the notion of sovereignty that resides with the people and reflects a commitment to a form of government that is responsive to the will of its constituents.