The parties to a contract can agree on the same thing in the same way, but simple consent is not enough, consent must also be free to complete the validity of a contract. Therefore, any influence that excludes free and intentional judgment is qualified as inadmissible influence. To conclude a valid contract, it is therefore essential that both parties have freely given their consent. For a valid contract to be maintained, it is essential to ensure the free consent of the parties. There is a concept of consensus ad idem which implies that the parties who conclude the contract must serve the same thing in the same sense. The agreement on the contractual conditions between the two parties should be on the same subject matter and on the same basis. The entire structure of contract law is based on the concept of consent, which is on the highest base during a contract.