How many Supreme Court Justices must agree to hear a case for it to be considered?

For a case to be considered by the Supreme Court, it requires the agreement of four justices. This is known as the "Rule of Four." This rule allows a minority of justices to grant a writ of certiorari, which is the means by which the Supreme Court selects most of the cases it hears. The reasoning behind this rule is to ensure that a significant number of justices believe a case has sufficient merit to be reviewed, even if a simple majority does not. This process helps to balance the desire to hear cases of national importance with the need to avoid an overwhelming caseload.