Abstract : It is an etablished fact that Thomas Aquinas's theory of freedom is not determinist; in each work, he grants to man the possibility to betake himself to contraries. Beyond all question, Thomas modifies his conceiving the freedom of man all along his teaching. In the commentary on Sentences, he grants primacy to free will: he grants it to be a discernment free from any restreint and any necesity. From De Veritate, Aquinas grants primacy to the voluntas, the appetizing and moving faculty of soul. Without minimizing the importance of free will, he makes it an act, that is to say the choice of free wil. In none of his works Thomas makes voluntas a paradigm. He nonetheless proposes an achieved definition of it. He distinguishes between polysemy and the notion of potentia and considers voluntas as being both a power and an act ; precisely he considers that will wants freely but in a natural way and chooses freely. In De Malo and Prima Secundae Pars he accurately theorizes the difference between the freedom of determining specifically and the freedom of exercising. In the final analysis Aquinas defines freedom as being the apanage of the act of the willing. He grants it being both a willful of having and desiring faculty of having the mastery of its acts and to be free from all necessities. Will is abble to want or not to want but Thomas does not show choice as a neutral act. Thomasian's greater innovations deal with the freedom increasing interest towards metaphysics and ethics. In Summa theologiae, the dominican roots ethical into a psychological freedom and inserts in a metaphysics of acting wich enablmes the realization of beeing. Freedom has to be considered at a time as a possibility to be realized, as as a power and an act in the progress of the way back to God. Therefore Thomas comes to a settlement that man is free to become free.