Answer:
The famous phrase emanating from the Declaration of Independence of the United States has not changed throughout history, thus remaining as the fundamental pillar that supports the national organization of the country, as it guarantees and aims the achievement and defense of the rights to life, liberty and the pursuit of hapiness. The phrase, like the entire Declaration of Independence, was authored by Thomas Jefferson and heavily influenced by the British philosopher John Locke.
Now, the interpretation of this phrase has changed over the years. Thus, for example, the right to life has undergone various changes in its integration, with states passing laws that allow abortion or legislating on euthanasia, for example. The same is true of freedom, where states variably regulate the various freedoms of their citizens.