In law, the process of analogical reasoning appears to work in five simple steps. (1) Some fact pattern A – the ‘source’ case – has certain characteristics; call them x, y, and z. (2) Fact pattern B – the ‘target’ case – has characteristics x, y, and q, or characteristics x, y, z, and q. (3) A is treated a certain way in law. (4) Some principle or rule, announced, created, or discovered in the process of thinking through A, B, and their interrelations, explains why A is treated the way that it is. (5) Because of what it shares in common with A, B should be treated the same way. It is covered by the same principle. It should be clear that the crucial step, and the most difficult, is (4). Often analogical reasoning works through the use of incompletely theorized agreements, making (4) tractable. Some of the disputes about analogical reasoning reflect contests between Burkean and Benthamite conceptions of law.
Sunstein, Cass R, Analogical Reasoning (October 7, 2021).