Passage Summary: Laws are meant to stop bad behavior by threatening punishment, but since you can't catch everyone if there are too many rules, a legal system should only focus on the worst crimes.

Conclusion: A successful legal system should only prohibit a small number of behaviors that are considered absolutely intolerable.

Reasoning: Laws work through deterrence, which requires a credible threat of punishment; however, the ability to catch and punish people decreases as the number of prohibited acts increases.

Analysis: The statement in question is the opening sentence, which defines the 'purpose of a law.' In the context of this argument, it serves as a foundational premise or a starting principle. The author uses this definition to build a chain of logic: if the purpose is X, and X requires Y, and Y is hindered by Z, then we must avoid Z. Since the statement provides the 'if' that starts the whole chain, it is a premise supporting the final recommendation. Look for an answer that identifies it as a general principle or a premise used to justify the conclusion.