A contract can be deemed void if:

A contract is a legally binding agreement that requires certain elements to be valid. One of those essential elements is a legal purpose. If a contract lacks a legal purpose, it cannot be enforced and is therefore deemed void. This means that even if all parties involved agree to the terms, if the content of the contract is illegal or contrary to public policy, it will not hold up in a court of law.

For instance, if a contract is for the sale of illegal drugs, no matter how much the parties agree or how well it is structured, it is void due to its illegal purpose. This understanding is fundamental in contract law, emphasizing the importance of legality in the formation of enforceable agreements.

In contrast, the other choices revolve around characteristics of a contract that do not inherently influence its validity. Simply having all parties agree to the contract, signing it, or having witnesses present does not guarantee that the contract is legally enforceable if it lacks a legitimate purpose.