“The world is all the richer for having a devil in it, so long as we keep our foot upon his neck.”

Simplified Meaning:

This quote means that the presence of evil or bad things can actually make the world better in some ways, as long as we keep them under control. Think about it like this: in a garden, weeds can pop up, but dealing with them helps the gardener become better at keeping the plants healthy. The weeds, or bad things, push us to be more careful and stronger. For example, in history, when there are problems like wars or diseases, people find new ways to solve them, and society can improve. It’s like how during a difficult time, people invent new medicines or come together to help each other. The idea is that these negative things can push us to learn, grow, and be better, but only if we don't let them take over our lives. So, in your own life, when you face challenges or difficult people, use those situations to become stronger and wiser. Don’t let the bad things control you; instead, use them to become a better person. This way, the presence of evil or trouble can actually make your life richer and more meaningful.