In contract law, for a contract to be valid, it must not:

For a contract to be valid and enforceable, it must not contradict public policy. Public policy refers to the principles that underpin the legal framework of a society and encompasses laws that reflect societal values and interests. When a contract is found to conflict with public policy, it can be declared void and unenforceable.

For example, a contract that requires an individual to engage in illegal activity or one that restricts personal freedom contrary to societal norms would be considered against public policy. Therefore, ensuring that a contract aligns with these overarching legal and ethical standards is crucial for its validity.

The other options refer to aspects of contracts that are either necessary for validity or not limiting factors. A contract must be legally binding and have a legal purpose to be valid. Additionally, while some contracts must be written to meet certain statutory requirements (like real estate transactions), not all contracts need to be in written form to be valid. Hence, a contract that contradicts public policy stands out as fundamentally flawed and unenforceable.