The most important part in analyzing moral concepts includes those used as predicate in moral sentences covering moral concepts of valuation and obligation. Moral concepts in the field of values include those like “good” and “bad” while obligatory concepts include “ought to” and “ought no” and “duty”. Many papers have been written about “moral obligation”; however, dissociating the area of semantics from ontology of the concept of “moral obligation”, this paper has proposed a new interpretation of Allame Tabatabaie’s viewpoint about semantics of “moral obligation”. This study intends to prove that for Allame Tabatabaie, the meaning of “moral obligation” is known as “necessity by the other” because he founds i’tibaryat theory based on “Sakkaki`s view” and there is no distinction between literal meanings of these kinds of metaphors from their real meanings, but figurative meanings are different from real meanings. Therefore, the meaning of “ought to” would not be different in real and credit usages and according to the fact that from his viewpoint the meaning of “real ought to” is “necessity by the other”; thus, the meaning of “credit ought to” will be “necessity by the other”, too.