Argument from Analogy

Arguing that governing a country requires gradual course changes because it resembles steering a large ship is an argument from analogy: shared features support a further conclusion. Such a comparison can help explain an idea or support a plausible conclusion, but it is not a proof. For example, enjoying a director's earlier films might give you a reason to try a new one, while changes in genre or collaborators could weaken the comparison. Ask this: are the similarities relevant to the particular conclusion, and what important differences might defeat it?

An argument from analogy works by identifying shared properties between two subjects to infer an additional shared property. The strength of the argument depends on relevant similarities, relevant differences, and the background assumptions connecting them to the conclusion. A strong analogy can illuminate a complex idea, while a weak one can be dangerously misleading.

To evaluate an analogy, consider three factors:

• Which properties or relationships the two things share; a long list of irrelevant matches adds little support.
• The relevance of those shared properties to the conclusion.
• The presence of critical differences (or "disanalogies") that might undermine the comparison.

For example, a startup might pitch investors by saying, "We are the Uber for dog walking." This comparison highlights an app-based, on-demand business model. If the startup uses that resemblance to predict comparable success in pet care, it is making an argument from analogy. The strength of this pitch depends on whether the similarities between the two markets are more significant than the differences (e.g., trust, logistics, regulation).

In law, lawyers often use analogies to argue that a new case is like a past one, so the same legal ruling should apply. In your personal life, you might reason that because learning guitar required daily practice and patience, learning to code will require a similar commitment. The key is to examine whether the comparison holds up to scrutiny or if it's a "false analogy" that obscures more than it clarifies.

Analogical comparisons can generate explanations or support tentative conclusions, but these uses should not be confused with deductive proof.

• Gentner and Markman (1997) describe analogy and similarity as involving structural alignment and mapping between representations, highlighting systems of relational correspondences rather than counting object matches alone. [1]
• Bartha's2019 archived entry distinguishes analogies from arguments based on them and discusses how similarities, differences and background considerations bear on the plausibility of an analogical inference. [2]
• Gentner (2016) reviews evidence that relational language and comparison can help learners attend to shared relations; this supports a role for analogy in learning without establishing that analogy accounts for all human thought. [3]

Analogical arguments can support plausible conclusions without making those conclusions certain. A comparison can omit an important difference or treat an irrelevant shared feature as decisive. For example, two services may both use an app yet face different trust, logistics or regulatory constraints, so success in one market does not establish success in the other. Ask what independent evidence would test the transferred conclusion and where the analogy stops applying.