Answer: written by Thomas Jefferson in The Continental Congress adopted the Declaration of Independence on July 4, 1776. It was engrossed on parchment and on August 2, 1776, delegates began signing it. 1st main idea The introductory sentence states the Declaration's main purpose, to explain the colonists' right to revolution. In other words, “to declare the causes which impel them to the separation.” Congress had to prove the legitimacy of its cause. It had just defied the most powerful nation on Earth. 2nd main idea The second portion of the document describes how King George III disregarded those natural rights to establish a tyranny over the colonies and sets up a justification for American independence. Its goals were to rally the troops, win foreign allies, and announce the creation of a new country. The introductory sentence states the Declaration's main purpose, to explain the colonists' right to revolution. In other words, “to declare the causes which impel them to the separation.” The Declaration of Independence was written to explain why the colonists were declaring independence from Great Britain and why the colonists had a right to do so.