Hello, "Common sense" means good judgment and decisions based on a simple observation of facts. It also is used to mean the intelligence that everyone should have. It does not depend on education, advanced degrees, etc. When someone tells you to look before you cross the street, or not to touch a hot stove, they might say "It's just common sense!" "Prevail" in this context means to win. He hopes that ridiculous or extreme decisions do not prevail (are not made by experts). "To hope common sense prevails" is a phrase often heard or read when a decision has to be made and one is hoping that the people making the decision do not do something foolish. Hope that helps! Best, Martha