Law has been defined as a "system of rules", as an "interpretive concept" to achieve justice, as an "authority" to mediate people's interests, and even as "the command of a sovereign, backed by the threat of a sanction". The numerous ways law might be thought of reflects the numerous ways law comes into everyone's lives. Contract law governs everything from buying a bus ticket, to obligations in the workplace. When buying or renting a house, property law defines people's rights and duties towards the bank, or landlord. When earning pensions, trust law protects savings. Tort law allows claims for compensation when someone is injured or has their property damaged. But if one person harms another intentionally, then criminal law ensures that the perpetrator is removed from society. Society itself is built upon law. Constitutional law provides a framework for making new laws, protecting people's human rights and choosing political representatives. Administrative law allows ordinary citizens to challenge the way government bodies exercise their power. Between different societies, international law build bridges, so that people everywhere can lead better lives. "The rule of law," wrote the philosopher Aristotle in 350BC, "is better than the rule of any individual.