John Locke made significant contributions to philosophy and political theory through his seminal works, particularly "Two Treatises of Government." He argued for the principles of natural rights, claiming that individuals possess rights to life, liberty, and property. Locke's social contract theory asserts that governments derive power from the consent of the governed, emphasizing the importance of individual freedom and responsibility. His ideas laid the groundwork for modern democratic thought and influenced the Founding Fathers of the United States, shaping the development of constitutional government.