One of the muslim philosophers' solutions for the problem of evil is that"a) It is privation of an entity; then it is evil by itself, such as: darkness, poverty, ignorance and etc.b) evil is of two kinds: It is an entity ; then it is evil by accident, that is, it is evil because it redounds to "a", such as: earthquake, storm, microbe and etc. But as non-entities have no cause, so evils are not created by God and ascribed to Him."But one of the evils is "pain" and its nature (i.e whether is it an entity or non-entity?) and that" is it evil by itself or by accident? " has been disputable among philosophers and theologians. Some of muslim thinkers have regarded it as contradictory to above solution. The aim of this article is:I. Survey of nature of pain - specially critique of Molla-sadra, s doctrine about this–and response to this question that " is pain evil by itself or by accident?"II. Presentation of my point of view about evils and pain: none of the evils are eviles by itself but contrary, all of them are evils by accident and there is only one evil by itself, that is pain, since the other evils are evils as such, because they redound to pain and likewise it is an entity not mere privation.