This Declaration is the very first official document where the term “happiness” appears as a principle for guiding good government. However, the document does not define “happiness”—it simply lionizes its “pursuiti.”
There has been much speculation as to why the Founding Fathers chose these terms—what appear, at first sight, to be vague, subjective ones—in such a crucial document rather than use John Locke’s terms from his Two Treatises of Civil Government (1689). Locke wrote that a principle of such government is: “Being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions.” The Founding Fathers left no written documents behind about their choice of words, replacing the term “possessions” by “Pursuit of Happiness.” This, in contrast to documents they left behind debating Ancient Greek Philosophers’ and historians’ debates about constitutions and checks and balances.
Some have speculated that the word choice might relate to the fact that African Americans were still slaves in 1776 and not “fully”—but only “fractionally”—American. Because they were themselves “possessions,” pairing that word with the promise of “life and liberty” might not have made sense. The vague term “happiness” might have been politically convenient as a way of avoiding sharp questions.
My own explanation is different, and gives the Founding Fathers far more credit. It has to do with the observation that the eighteenth century saw much debate about crucial words in political vocabulary that seemed to be losing their traditional meaning.
Recall that the word “happiness” derives from “hap” which means chance, fortune, and is associated with randomness. In French too, the word “heureux”—used today to mean “happy”—comes from “heur,” which in older French meant chance or fortune. This connection is still reflected in the term “malheur,” meaning misfortune and unhappiness, the opposite of “bonheur,” which translates to “happiness.” In Latin, too, “felix” referred to both “happiness” and “luck”; In modern German, the word is Glück for both happiness and luck, a dual meaning found in other European languages to this day. In Polish, “szczescie” is used for both, sharing roots with the Serbo-Croat “sreca,” Hungarian “szerencse” (luck) bearing affinity to Czech (“stesti a stesti”); In Estonian too the same word “onne ja onne” is being used for these two terms.