During the time when the church controlled what people could believe, and the kings ruled over what people ought to own, John Locke, an English doctor, popularized three ideas that changed society and parenting forever. First, people keep fighting over their beliefs, because nobody can actually know which one is true. To solve this problem, everyone should have freedom of thought and the right to choose their own religion. Second, kings can't just do as they please, because people have natural rights to liberty, property and life, and hence need to be asked for permission. Third, parents should avoid punishing their children, since the use of emotions to make them behave well can make them sensationalist. Instead, they should allow their children to be guided by thoughts. Locke's idea on religion and democracy became the foundation of most liberal societies. His thoughts on education, however, may have been even more influential. Locke understood that most people doubt new ideas, without any other apparent reason than them being uncommon. However, teaching children how to think rationally and all for themselves works. Education is therefore the key to freeing society from political and psychological tyranny. And his book. Some Thoughts Concerning Education, became a parenting guide to that world.