Which of the following is a necessary element for a contract to be considered valid?

For a contract to be considered valid, it is essential that it has a legal purpose. This means that the contract's terms and provisions must be legally permissible and cannot involve illegal activities or violate public policy. If a contract's purpose is illegal, the contract cannot be enforced in a court of law. For example, an agreement for the sale of illegal drugs would not be considered a valid contract. Therefore, the legality of the contract's purpose is a fundamental requirement for it to be valid and binding.

While mutual understanding, a written agreement, and voluntary consent are important factors in creating a contract, they do not replace the necessity of having a legal purpose. Without this element, no contract can stand up to legal scrutiny, making it a cornerstone of contract validity.