Argument from analogy

You claim something about one case by pointing to a second, different case about which the same thing is already accepted. The argument works because the two cases are alike in the respect that matters here, so what holds for one carries over to the other. You can attack it by denying that the cases are alike in the way the claim requires. The argument then collapses without disputing anything about the second case.

Example

Cycling on the grass is prohibited because walking on the grass is prohibited

Kolb, R. (2016). The law of treaties: An introduction (p. 152). Cheltenham: Edward Elgar Publishing.

Standardised form

Cycling on the grass (a) is prohibited (X) because walking on the grass (b) is prohibited (X).

Transformations applied: none — the example is already in canonical form.

Classification

The subjects differ and the predicate is the same, so the argument form is beta (a is X because b is X).

The conclusion is about one specific activity (s) and the premise about one specific activity (s), so the argument substance is ss.

The keyword ANALOGOUS describes the relationship between subjects a and b. The argument lever can thus be formulated as “Cycling on the grass (a) is ANALOGOUS to walking on the grass (b)”.

Not to be confused with

• Argument from similarity — Substance in the alpha sense: a factual claim supported by a factual one. F ← F
• Argument from comparison — An evaluation supported by an evaluation. V ← V
• Argument from equality — A policy claim supported by a factual one. P ← F
• Argument from example — Substance, not lever: the conclusion is about a whole class and the premise about one member of it. us

Notes

The literature often treats argument from analogy, argument from similarity, argument from comparison, and argument from equality as the same. In the PTA, “argument from analogy” remains a broad, umbrella label (much like “argument from sign” in the Alpha Quadrant). However, its parametric approach to argument categorization allows a more precise distinction among the other three argument types by using the distinction between statements of fact (F), value (V), and policy (P) used to determine the value of argument substance in the Alpha Quadrant. Applying these labels, it turns out that, typically, the argument from similarity has an F-claim supported by an F-claim; the argument from comparison has a V-claim supported by a V-claim; and the argument from equality has a P-claim supported by an F-claim.