Taa'rud means conflict. In Usul al Fiqh, Taarud means that two evidence of Shariah are of equal strength and they seem in opposion of each other. A conflict is thus not expected to occur if the two evidences are of unequal strength, because the stronger evidence will prevail. For this reason, there will be no conflict between a Qati and Zanni proof.
If, however, the opposite is required by 2 Quranic Ayat or by a Quranic Ayat and a Mutawatir Hadith (these two are considered equal in authenticity as explained earlier in the discussion) or by two Ahad Hadith (difference of opinion in this), then, there is a conflict.
Conflict can only arise, if the rulings of the two evidence can not be reconciled. This means that the subject matter of one can not be distinguished from the other or the time sequence of them can not be distinguished (that is it can not be ascertained which one is the latter).
A genuine conflict can hardly arise between Qati proofs. All such conflicts are apparent rather then real. Such apparent conflicts can be resolved by
by specification or
by giving preference of one over the other.
A conflict between Nasus (texts of the Quran and the Sunnah) and Ijma is inconceivable as Ijma can not violate Nass.
A Mujtahid must therefore, try to reconcile the apparent conflict in which case both the evidence will be applicable in different sets of circumstances. If this is not possible, he will try to prefer one over the other, thus at least one evidence will be kept. If this is not possible, then, he would see the time sequence and apply the principle of abrogation.
In this way the later evidence will be retained and the earlier one in time will stand abrogated.
(However such cases are very few. Please see Naskh discussed earlier).
If this is also not possible, both the evidences will be abandoned. When two evidence in conflict are Amm (general), one may try to distinguish the subject matter of application (for instance one may be applicable to adult and the other to the minor or one may be applicable to married people and the other to unmarried people.) If one evidence is Amm and the other Khass, the solution is Takhsis al Amm (specification of a part of Amm).
As regards, cases where both the rulings can not be retained because of apparent conflict, the following rules of preference should be applied :
Clear texts will be preferred over unclear texts
Sarih will be preferred over Kinayah, Haqiqi over Majaji and so on.
Mutawatir Hadith will be preferred over Mashhur and Mashhur will be preferred over Ahad.
Hadith transmitted by Faqih or leading companions are preferred over others.
Another rule of preference is that affirmative rule takes priority over negative.
Similarly prohibition takes priority over permissibility.
If attempts at reconciliation or preference fail, then resort should be taken to abrogation (Naskh).
Rules or view points on Naskh may be seen in earlier discussion.
In the case of conflict of two Qiyas, if the two can not be reconciled, one may be given preference.