Now, if we find that the Lawgiver has issued a ruling without disclosing its cause, while He has in fact identified the cause for a comparable ruling or for another ruling of the same kind, the matter is different.

Consider the case in which He allowed a father to marry off his young, virgin daughter without her consent. We also see that He allowed that same father to take charge of her property because she is a minor. Should we therefore assume that minority itself is the operative cause in the sphere of marriage, just as it is in matters of property? Or might we say that marriage could have a separate cause—her virginity, for example? In that event, virginity would be the effective factor: the Lawgiver has shown its influence in one explicit text yet remained silent about its influence in the parallel ruling.

The first two schools accept this line of reasoning, which in truth amounts to establishing the cause by analogy: just as the attribute produced the ruling in the cited instance, it produces it in the similar instance as well.

The third school, however, does not endorse such reasoning unless supported by a specific indicator, since a single category of rulings may well have multiple causes.

A practical example: the Prophet—may blessings and peace be upon him—forbade a man to sell over his brother’s sale, to bid over his brother’s bid, or to propose marriage over his brother’s proposal. He explained that the rationale is the discord this sows among people. The same rationale is invoked in his statement: “Do not marry a woman together with her paternal aunt, nor with her maternal aunt, for if you do so …”