Something is claimed 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, which collapses the argument without disputing anything about the second case.
Example
Cycling on the grass is prohibited because walking on the grass is prohibited
Standardized 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)”.
Assessment questions
- Is walking on the grass indeed prohibited?
- Is cycling on the grass analogous to walking on the grass with regard to what the prohibition is meant to achieve?
- Is the prohibition on walking enough to conclude that cycling is prohibited too, or are there relevant differences — speed, damage, safety — that would justify treating the two differently?
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.
Source of the example
Kolb, R. (2016). The law of treaties: An introduction (p. 152). Cheltenham: Edward Elgar Publishing.
