The law pervades American life, but few of us have a clear understanding of what the law is. Simply put, the law is established rules of conduct. Through the law we are able to know what our rights are, what our duties are, and what our privileges are. We use this understanding to regulate and conform our conduct.

The law allows us to predict the consequences of our actions and to order our conduct accordingly, when three characteristics are present:

• Stability. For the law to be an effective guide to conduct, it must be stable. Frequent changes in the goals and purposes of the law breed uncertainty and make the law ineffective as a guide to conduct.

• Predictability. The law allows individuals to predict the consequences of their actions. We expect that similar actions will result in similar consequences.

• Flexibility. The law must advance as circumstances change. Our system of law must take into account social, scientific, technological, and economic changes when evaluating the consequences of specific actions.

The American legal system is modeled on the English common-law system of law, which rested primarily on a single set of laws and a single court system. The American legal system is considerably more complicated, involving the interplay between a written constitution, national legislation, administrative rules, and a strong common-law tradition.

To make matters worse, each of the four sources of law in the American legal system — constitutional, statutory, administrative, and common law — are found at both the state and federal level. Each of the four sources of law can have a significant effect on how the law guides conduct.