Analogical Reasoning
Analogies in Arguments
Dissect real-world arguments built on analogy -- from legal precedent to policy debates -- and develop rigorous criteria for evaluating when an analogy strengthens or undermines a case.
Context
Why this exercise
Most consequential arguments in public life lean on analogies. Lawyers reason from precedent; policymakers compare new technologies to old ones to decide how to regulate them; doctors explain treatment options through illness narratives borrowed from other patients. Each of these moves carries the same risk: the analogy can either illuminate the actual structure of the problem or smuggle in conclusions through a back door. This exercise drops you into realistic argumentative settings — legal precedent, tech policy, medical communication — and asks you to perform the analyst's core task: judge whether the analogy supports the conclusion being drawn or whether it has been stretched past its load-bearing limit.
Before you start
Argument by analogy has a long history in formal logic. Aristotle treated it as a species of induction, and modern logicians from Irving Copi onward have given it explicit evaluation criteria: relevance of shared properties, number of shared properties, number of disanalogies, strength of the conclusion relative to the premises, and diversity of the analogical instances. The cognitive science side comes from Dedre Gentner's Structure-Mapping Theory and Douglas Hofstadter's work in 'Surfaces and Essences,' both of which emphasize that strong analogies map relational systems rather than isolated attributes. In legal scholarship, Cass Sunstein and Scott Brewer have shown that the choice of abstraction level in an analogical argument effectively determines the outcome: framing a precedent narrowly limits its reach, framing it broadly extends it, and the actual judicial work happens at this framing step.
The common failure modes in analogical argument are predictable enough to catalogue. Surface-feature mapping confuses verbal or aesthetic similarities with structural ones — a 'toxic workplace' and a 'toxic chemical' share the word, not the legal category. Selective mapping cherry-picks the features that support the conclusion and ignores the features that would undermine it. Domain transfer errors carry conclusions across domains that differ in exactly the dimension the conclusion depends on — household budgeting fails for sovereign-currency governments precisely on the dimension of monetary authority. And the 'apples to oranges' dismissal, which Robert Jay Lifton classified as a thought-terminating cliché, defeats an analogy without doing the analytical work of explaining which differences are relevant and why.
When evaluating any analogical argument, force the speaker (or yourself) to name the mapping explicitly: what property of A corresponds to what property of B, and what conclusion is supposed to follow from that correspondence. Then ask the diagnostic question: does the analogy break down on the specific dimension the conclusion depends on? A bridge analogy can usefully transfer load-distribution principles even if the bridges differ in material; the analogy fails only if the differing material changes the load behavior. The same surgical approach applies to every legal precedent, regulatory comparison, and 'we are the Uber of X' startup pitch. For the underlying framework, see Argument Analysis, which treats premise-conclusion structure in depth.