American government is a product of numerous Enlightenment thinkers, who thrived in the late 17th and early 18th centuries. These include the English philosopher Thomas Hobbes. While some of Hobbes' ideas were contrary to American governing principles -- like his belief in absolute power over a government's subjects -- many were perfectly consistent with the ideas presented in the country's founding documents. While many of his ideas on social contracts, equality and natural liberties inspired the Declaration of Independence and the Constitution, others were not truly integrated into the U.S. philosophy of government until after the Civil War.
When John Hobbes imagined what life would be like without government, he concluded it would be "nasty, brutish, and short." He envisioned individuals constantly vying with each other for their own self-interest and attacking others in pursuit of those interests. From this pessimistic view comes a foundation of American government rooted in Hobbes: the social compact. Hobbes believed that to enforce law and prevent the chaos of the state of nature, people consented to forming a government. This idea is written into the preamble of the U.S. Constitution, when "We the People" establish a government to do things like "ensure domestic tranquility" and "promote the general welfare."
When the Declaration of Independence was written, it specified that "all men are created equal, and endowed... with certain unalienable rights." While this idea also comes from the philosopher John Locke, Thomas Hobbes contributed significantly to the idea of natural liberties as well. Significantly, Hobbes believed that all subjects of a government had the right to defend themselves against, and even overthrow, a government that no longer supported them. This, of course, is the foundational idea behind the Declaration of Independence and the establishment of the United States. Furthermore, the Second Amendment to the Constitution, which states that a well regulated militia is necessary to the security of a free state, supports a Hobbesian view on self-defense.
Equality of All Men
Hobbes' governmentless world did have one advantage: All people were inherently equal. In fact, their equality of capability was partly what made life so terrible, because no single person was ever able to rise above anyone else. Hobbes thought equality needed to be protected, and U.S. government has evolved to more firmly embrace the concept of equality. After the Civil War, the adoption of the 14th Amendment, for example, forbade any jurisdiction from denying a person equality before the law. Before that, the Declaration of Independence, which stated that all men are created equal, provided only a conceptual foundation for equality in government.
Life, Liberty and the Pursuit of Happiness
Hobbes believed that the tendency towards self-preservation was a natural instinct and should be a cornerstone of governing principles. In American government, the principle was first stated in the Declaration of Independence as the fact that all men are entitled to life, liberty, and the pursuit of happiness. While this statement also has Lockean influence, the mention of "life" is particularly Hobbesian, because Hobbes thought preserving one's own life was sacrosanct. In the U.S. Constitution, the post-Civil War 14th Amendment explicitly forbids any state from depriving a person of life, liberty or property without due process of law. This enshrined Hobbesian ideas into U.S. government.