Final answer:
The passage is from the Declaration of Independence, and the three unalienable rights mentioned are Life, Liberty, and the pursuit of Happiness.
Step-by-step explanation:
The passage quoted is from the preamble of the Declaration of Independence, which outlines the philosophy of natural rights and the purpose of government as envisioned by the Founding Fathers of the United States. The three rights that the writers claim as unalienable, meaning they cannot be taken away or denied, are Life, Liberty, and the pursuit of Happiness. These rights are deemed inherent to every person and are the foundation for the establishment and operation of any government.