Commonsense and rational fundamentals plus a number of similar words have been repeatedly used by the Muslim juristconsults, conservatives, and jurists in their books as well as their treatises on jurisprudence, theology and Islamic law. Commonsense, by denotative definition, means something known, that comes opposite to an unknown thing. Connotatively, the word refers to a rule that comes from the people, is all-embracing and sustainable, and abiding by which has been necessitated by the competent authority.
The question is this that whether rational commonsense is valid in view of the Sharia law and in view of the Imamiyah school of thought. Is it legal to act upon rational commonsense or not? What is the correlation between commonsense and Sharia law?
As far as the correlation between Sharia law and commonsense is concerned, there are three hypotheses: the commonsense is approved by the Sharia law; the commonsense is denied by the Sharia law; the commonsense enjoys no views by the Sharia law either approving or rejecting it. In this case, there is no access to Sharia text on commonsense, thus its validity shall be a source of discord: It is valid unconditionally; it is valid through the principle of decency and obscenity; it is valid at the endorsement of the legislator, either direct endorsement or approval as non-denial, otherwise it shall be deemed unacceptable.
Imam Khomeini believes in the inherent competence or validity of the commonsense but conditions it to the endorsement or no-denial. However, he argues that the legislator’s endorsement assures the rationality of the commonsense. Sheikh ul-Sharia of Isfahan argues that ratification of no-denial is not necessary, and lack of ascertainment of what has been denied shall be sufficient.