What may happen to one thing is stated by reporting what actually happened to another thing of the same sort. The argument works because the earlier case did turn out this way, and the present case is held to be enough like it for the same outcome to be open. You can attack it by showing that the two cases differ in whatever made the earlier outcome possible.
Example
It is possible that the Tories will recover from their bad position because Labour recovered from their bad position in 2019
Standardized form
The Tories (a) can possibly recover from their bad position (X) because Labour in 2019 (b) recovered from their bad position (X).
Transformations applied: the opener “it is possible that” absorbed into the conclusion predicate; the date moved into the premise subject, so that “in 2019” identifies which Labour is meant rather than trailing the predicate.
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 party (s) and the premise about one specific party (s), so the argument substance is ss.
The keyword SIMILAR describes the relationship between subjects a and b. The argument lever can thus be formulated as “The Tories (a) are SIMILAR to Labour in 2019 (b) with respect to possibly recovering from their bad position (X)”.
Assessment questions
- Did Labour indeed recover from their bad position in 2019?
- Are the Tories similar to Labour in 2019 in the respects that made Labour’s recovery possible?
- Is Labour’s recovery enough to conclude that the Tories can recover too, or do differences — leadership, the electoral landscape, the causes of their bad position — make the two cases diverge?
Not to be confused with
- Argument from analogy — The likeness is one of relations: elements of the one case stand to each other as elements of the other case do, rather than the two cases sharing the properties that make the outcome possible.
ANALOGOUS - Argument from comparison — The two cases are set side by side and measured against each other, rather than one being taken as a precedent for the other.
COMPARABLE - Argument from equality — The two cases are claimed to be entitled to the same treatment, not merely to be alike.
EQUAL - Metaphoric argument — The second case is not a real comparable at all but a figure of speech.
METAPHORICALLY
Other examples
- “Nearly everything we had in the past (b) was recyclable (X), so nearly everything we have in the future (a) may be recyclable (X).” — source not yet recorded. “Establishing gun control in the present-day U.S. (a) will lead to genocide (X) because establishing gun control in historical Germany (b) led to genocide (X).” — adapted from a campaign ad featuring Joe Wurzelbacher, published on YouTube as “Joe the Plumber Ad: Gun Control Caused Holocaust”. “Mars (a) may be inhabited (X) because the earth (b) is inhabited (X).” — adapted from Reid, T. (1785). Essays on the intellectual powers of man (Essay I, ch. IV, p. 24). Edinburgh: John Bell.
Notes
In the literature, the argument from similarity is often not distinguished from the argument from analogy. In the PTA the two are distinct types: the argument from similarity transfers the predicate on the strength of properties the two cases share, the argument from analogy on the strength of a correspondence between the relations that hold within each case. Reid’s planetary example, listed under Other examples, is the classic textbook case: Reid lists the properties the planets share with the earth — they revolve around the sun, borrow their light from it, rotate on their axes, some have moons, all are subject to gravitation — and concludes that they may be inhabited too. The original speaks of Saturn, Jupiter, Mars, Venus and Mercury together; it has been reduced to Mars so that the substance stays ss. Reid gives no reason why the shared properties bear on being inhabited, so the lever is asserted rather than supported, which is why the argument is usually judged no more than minimally plausible (see Bartha, P.F.A. (2024). Analogy and analogical reasoning. The Stanford Encyclopedia of Philosophy, Fall 2024 edition).
Source of the example
Adapted from an article in The Guardian. The article is not identified on the type page; full citation not yet recorded.
