What are the four sections of the Declaration of Independence?

The four sections of the Declaration of Independence are as follows. I have included a brief summary of each section.

The first section, or the Preamble, states the purpose of the document. It says, in short, that the American colonies are about to assume their "separate and equal station" among the nations of the world and that this is such a drastic and significant action that they owe it to the rest of the world to explain themselves. 

The second section consists of a statement of principles. This is perhaps the most famous section of the document, in which Jefferson proclaims such "self-evident truths" as the fundamental equality of all men and the "unalienable rights" to which they are all entitled, which include "life, liberty, and the pursuit of happiness." They further assert that the purpose of government is to secure these rights, and that when government "becomes destructive of these ends," the people have the right to rid themselves of it and establish another government that will be more attentive to their rights.

The third section is a list of grievances, a "history of repeated injuries and usurpations" which the colonists lay squarely at the feet of King George III. These grievances include refusing to approve laws which would benefit the colonies, dissolving colonial assemblies (through his representatives, the royal governors), keeping standing armies in the colonies in time of peace, and "imposing taxes on us without our consent." Moreover, the colonists charged, he had incited the "merciless Indian savages" to make war on them. Interestingly, Thomas Jefferson wanted to include a passage that blamed King George for instituting slavery, or at least the slave trade, in the colonies, but delegates from South Carolina and Georgia struck out this passage when it went before the Congress. 

Finally, there is the actual declaration of independence itself. At the end of the document, the signers declared that all "political connection" between the colonies and Great Britain was "dissolved," and declared their intent to proceed as free and independent states.