Procedural Principles (Arabic: الأصول العملية; Usul al-Amaliyya) are the principles that are used in a situation of doubt; they form a kind of fall-back position in the absence of legal evidence. They are an important means through which divine-law rulings can be stipulated when no clear substantiating evidences exist in either the textual or non-textual sources of law.
See main article: Ihtiyat
The principle of precaution is the first and foremost principle. This principle is applied in a case where there is only partial knowledge about the law; that is, in cases of Ilm al-Ijmali - where there is a semi-doubt and a semi-certainty. In a situation of doubt, one must observe precaution and if there is a possibility of something being impermissible, one should avoid it. If there is a possibility of it being an obligation, one must follow it.
See main article: Bara'ah
The principle of non-obligation or principle of exoneration is considered as a basic and primary rational principle. This principle states that, in a situation of doubt, things are assumed to be permissible until proven otherwise. Traditional scholars of usul considered it to be an act of injustice on the part of Allah to hold somebody responsible for that which they do not know. This rule is applied in a case which has not been mentioned, explicitly or implicitly, in the sources of the shari'ah.
See main article: Istishab
The principle of continuity operates when a person was in certainty about some state of affairs, and then doubts whether or not that state of affairs is still the case. The principle dictates that they assume that the state of affairs still holds true. For example, if a person did their ritual washing, and then doubts if they have done something to break their state of ritual purity, they should assume they are still in that state until proven otherwise.
See main article: Takhyir
The principle of choice is applied in cases similar to that of ihtiyat, that is, semi-doubt and semi certainty. However, the principle of choice is applied where it is not possible to act on both sides of the issue.
- Procedural Principles of Ijtihad by Sayyid Muhammad Rizvi