How many justices must agree in order for a decision to be made by the Supreme Court?

The Supreme Court requires a majority of justices to agree in order to render a decision. This means that if there are nine justices on the Court, at least five must be in agreement for a case to be decided. This standard ensures that there is a clear and decisive ruling, which is essential for maintaining the authority and functionality of the judicial system. Decisions made by a majority also reflect a balance between differing viewpoints among the justices, contributing to the development of case law and legal precedents in the United States.

Other options do not apply to the decision-making process of the Supreme Court. Requiring all justices to agree would hinder the possibility of reaching a decision, especially if there are dissenting opinions. A quarter or two-thirds majority would also create confusion, as the established rule is firmly based on a simple majority for clarity and consistency.