A useful way to analyze a purported analogy is to identify:
1. Asl: the established original case, such as wine.
2. Its hukm: the original legal ruling, such as prohibition.
3. ‘Illah: the intoxicating property that explains the ruling.
4. Far‘: another substance genuinely possessing the same property.
These four headings help us organize the comparison. The textbook singles out the ‘illah as the pillar of qiyas, because it supplies the legally meaningful connection. Without an established common cause, the proposed extension remains unsupported.