What is the main conflict in Two Treatises of Government by John Locke?

Two Treatises of Government is the book in which John Locke explains his concept of modern liberalism. In this book he expresses his belief that the purpose of political societies is to defend the life, liberty and property of citizens of that society. The only source of authority for a government is from the people. When a government becomes tyrannical, then people have the right to stage a revolution against that government.