Does God allow evil according to St. Thomas Aquinas?

Actually God did not will Evil.God just permit it. He permits it for one reason.This reason is, God permits evil because He can draw good out of Evil.For example if there is calamity,do you the reason why god permits this? Authentically, God is not the one who made this God is just permitting it.Then we could ask our selves why God permits this.Is there good can draw from this situation? And the answer is,Yes there is, if we observed sometimes because of this situation we can see the spirit of generosity of some men by helping their fellowmen who are victims of calamities.So, still there is good that can draw even in the agony happening in our life.