John Locke is widely regarded as the father of liberalism due to his profound philosophical contributions that laid the groundwork for modern liberal thought. His ideas, articulated primarily in 'Two Treatises of Government,' challenged the prevailing notions of absolute monarchy and divine right, advocating instead for individual rights, limited government, and government by consent.

At the core of Locke's philosophy is the concept of natural rights, which he believed were inherent to all individuals by virtue of their humanity, not granted by any ruler or state. These fundamental rights include life, liberty, and property. He argued that individuals possess these rights even in a 'state of nature' before the formation of government.

To protect these natural rights, Locke proposed the social contract theory. Unlike Hobbes, who envisioned a contract leading to absolute power, Locke's social contract involved individuals voluntarily surrendering some of their rights to a government, but only to the extent necessary for the protection of their remaining rights. This government, therefore, derives its legitimacy from the consent of the governed. If the government fails to uphold its end of the contract by infringing upon natural rights, the people retain the right to resist and even overthrow it.

Locke was a strong proponent of limited government, emphasizing that its power should be constrained by law and accountable to the people. He advocated for a separation of powers, particularly stressing the supremacy of the legislative branch, which he believed should be closest to the people and responsible for making laws. His ideas on religious toleration, though not absolute, also contributed to liberal thought by arguing for the separation of church and state and the freedom of individual conscience.

Locke's philosophy profoundly influenced the Enlightenment, the American and French Revolutions, and the development of constitutional democracies worldwide. His emphasis on individual autonomy, rights, and limited government remains a cornerstone of liberal political theory, making him an indispensable figure in the history of political thought.