such as the harm caused by striking one’s parents, which is analogically compared to the mere utterance of taʾfīf (“uff”). If the effective cause is absent from the branch, the analogy is invalid.
A case in point: someone argues that the cause for the prohibition of usury in wheat is that it is sold by measure, then claims that usury applies to apples by analogy with wheat. This analogy is unsound, because the cause is not found in the branch: apples are not sold by measure.
Categories of analogy
Analogy is divided into manifest and subtle.
- The manifest (jalī): an analogy whose effective cause is established by a textual proof, by consensus, or where the absence of any relevant distinction between the original and the branch is categorically certain.
• An example whose cause is established by text: prohibiting the use of dry impure blood for istijmār (cleansing with solid materials) by analogy with the prohibition of cleansing with dung. The cause of the original ruling is confirmed by textual evidence: Ibn Masʿūd—may Allah be pleased with him—brought two stones and a piece of dung to the Prophet ﷺ to use for purification; the Prophet took the two stones, discarded the dung, and said, “This is filth.” (1) Filth here means impurity.
• An example whose cause is established by consensus: the Prophet ﷺ forbade a judge to issue rulings while angry (2). By analogy, a person in pressing need to relieve himself is barred from judging just as an angry judge is barred. This is manifest analogy, for the cause in the original—mental distraction and preoccupation of the heart—is affirmed by consensus.