legal status of the contract containing illegitimate subject in imāmī jurisprudence

there is disagreement among the imāmī jurisprudences concerning the legal status of contract containing illegitimate subject; although some maintain the soundness of such contract, most jurists believe in the invalidity and prohibition of acting on the illegitimate subject of the contract. among those maintaining the invalidity, some have accepted it as the primary rule and principle in these contracts and for proving it have relied upon the unlawful benefit as not being property, not having material value, lacking power to surrender, contradiction in religious law, and disclaiming the respect for unlawful property by the legislator. some others, by criticizing the viewpoint of the first group, have maintained the invalidity of such a contract according to such traditions as those of tuḥaf al-‘uqūl. in this article, we have addressed the viewpoints brought up in this respect and finally have proved the invalidity and unlawfulness of such a contract in a new way by means of criticizing all the viewpoints and disproving the reasons given