Liberalism is a theory that has affected political, social, economic, and other fields. It was conceived of by John Locke in Two Treatises on Government. It is the ideological foundation behind the concepts of liberty, equality, and free markets. Liberalism has had significant impacts on economic theory and politics and is a significant part of the United States government. Political liberalism is based on the ''harm principle'' as used by John Stuart Mill. It is likely the most popular and applied political ideology in the world. The central tenets of liberalism include: Liberty, Equality, Economic freedom, Rule of law, Limited government, Democratic government.
Political liberalism is a theory which states that limited government should have as its primary purpose the defense and procurement of the natural rights of its citizens. Both Democratic and Republican parties adhere to the tenets of liberalism. The chief difference between the different parties that adhere to liberalism is deciding what is a positive right.