One of the important issues which has always occupied man's mind is the contradiction between causal necessity and free will. The Confusion between will and choice, and wrong presentation of the problem of free will has immersed this issue in many ambiguities. Contrary to common conception, the central pillar of the problem is not the sequence of wills; rather, acceptance of causal necessity, and creation of will and its ending up to a cause outside man's soul directly create will in man's soul. The master of theosophers (Mulla Sadra) takes into consideration the main problem of determination in will and even accepts determinism of will and man's volitional actions. However, this does not mean that Mulla Sadra denies man's choice. Using the concepts of ‘agent by compulsion’ and ‘unity of divine acts’, he tries to explain that determination is in harmony with choice and man's acts are compulsory as they are volitional. Reconstructing the problem of free will, the present paper explains and criticizes Mulla Sadra's five answers to this problem. Finally, it concludes that causal necessity contradicts man's free will and choice, so accepting man's choice necessitates causal necessity denial