The issue of determination and free-will has long between the special concern of Muslim thinkers, and it has been stressed by the Glorious Quran and traditions. This idea was first mooted by Muslims in the first century ('AH'), and different views have been provided in this concern over the history. Attempting to preserve the principle of unification of act, Ash'arite theologians have adhered to determination neglecting divine justice and dismissing it but the expense of unification of act. The dispute between Mu’tazilah theologians over unification of act or divine justice ended in their adherence to divine justice, and so they questioned the unification of act when the introduced the idea of absolute delegation of power. Presenting the idea of "intermediate position" and preserving the principles of unification of act and divine justice, Shi’I school of thought has explained man's free-will in the light of divine agency. This view does not have the deficiencies which each of two previous ones has. The subtlety of the idea "intermediate position" has made theologians, philosophers and mystics provide several interpretations for it. Using a rational analysis method, the present paper elaborates on this issue, and shed light on the interpretation of "intermediate position", by commenting on philosophical determination and providing a solution for the question of succession of wills.