The basis of the arbitrator's power to hear disputes between parties is the "contract". The parties to the dispute stipulate in the main contract or separately that the arbitrator will resolve their disputes. However, the dispute between the parties may be in the main contract. That is, one of the parties claims the invalidity of the main contract and the other party believes in its validity. On this basis, the question arises whether the arbitrator can hear the dispute between the parties in the main contract. If we believe that the arbitrator has the authority to hear the validity or invalidity of the contract, if he rules on its invalidity, he has questioned the basis of his authority, which was the same contract. To resolve this problem, the theory of collateral contract has been proposed in arbitration, according to which the arbitration clause, whether it is included in the main contract or included as a condition in the contract, is considered an independent contract and the validity or invalidity of the main contract has no effect on the arbitration contract. This article examines this theory through a comparative study of Iranian, French, and English law and a library method, and based on the assumption that the arbitration clause is independent of the main contract based on the implicit consent of the parties. In the end, it has been concluded that the arbitrator has the authority to consider and decide on the validity and invalidity of the original contract. This is in accordance with the law and reflects the implicit intention of the parties to the dispute. The judicial practice of Iran and the countries of France and England has moved towards accepting the rule of independence of the arbitration clause from the original contract, and as a result, the arbitrator can consider the validity and invalidity of the contract and the cases of termination and annulment of the original contract, and in these circumstances, one of the obstacles to accepting arbitration as the most important alternative method of resolving disputes will be removed.