ArgLab • Colloquium

Luís Duarte d’Almeida

The Structure of Arguments by Analogy in Law

I discuss the structure of arguments by analogy in law. My working example is the case of Adams v New Jersey Steamboat Company.1 Adams was first cited as an illustration of ‘legal use of argument by analogy’ by Martin Golding; today it is the most discussed example of its kind.2 The issue in Adams was whether a steamboat company should be held liable for money stolen from a passenger’s room without negligence on the part of either the passenger or the company. The Court drew an analogy between steamboat companies and innkeepers, who owed a high duty of care and were liable for money stolen from a guest’s room:


“[T]he traveller who pays for his passage, and engages a room in one of the modern floating palaces that cross the sea or navigate the interior waters of the country, establishes legal relations with the carrier that cannot well be distinguished from those that exist between the hotelkeeper and his guests. The carrier in that case undertakes to provide for all his wants, including a private room for his exclusive use, which is to be as free from all intrusion as that assigned to the guest at a hotel. The two relations, if not identical, bear such close analogy to each other that the same rule of responsibility should govern. We are of the opinion, therefore, that the defendant was properly held liable in this case for the money stolen from the plaintiff, without any proof of negligence.”


In this paper I take issue with Golding’s own reconstruction of the logical structure of arguments by analogy. The reason I focus on Golding’s account is that it is the most well- known and influential attempt to articulate the structure of arguments by analogy within the frame of a very popular picture of analogical arguments. According to this popular picture, in an argument by analogy we compare at least two items. On the one hand, we have the source (or sources) of the analogy. On the other, we have the target. The target is what the argument by analogy is about. How does the argument proceed? There are a number of characteristics F, G . . . that are shared by both the source and the target. There is also some characteristic H that the source, but not the target, is known to have. An argument by analogy relies on the fact that source and target are alike with regard to characteristics F, G . . . to infer that they must also be alike with regard to characteristic H. The conclusion of the argument is that the target, too, has characteristic H.


Golding’s reconstruction of the Court’s argument in Adams presents it as an instance of the following scheme:


(1)        x has characteristics F, G . . .

(2)        y has characteristics F, G . . .

(3)        x has characteristic H.

(4)        F, G . . . are H-relevant characteristics.

(5)        Therefore, unless there are countervailing considerations, y has characteristic H.


I raise two worries with regard to this proposal. (These worries are not exhaustive of what I find problematic about this reconstruction of arguments by analogy in law.) The first worry is that premises (1) and (3) seem to be superfluous. Any instance of premise (4) can be restated as (or at least directly supports) a universal conditional affirming that for every x, if x has characteristics F, G . . ., then x has characteristic H. But then (5), the conclusion of the argument, can be derived from the combination of premises (2) and (4). That means that the conclusion of the argument can be established without any reference to the source or to its similarity to the target. How then could the scheme stand as a good reconstruction of arguments by analogy?


The second worry is specifically concerned with arguments by analogy in the legal domain. It regards the status of premise (4). Should it be read as a descriptive or a normative premiss? (In Adams, should it be understood as the premiss that the reason why innkeepers were held liable is that they provided rooms to guests in such conditions that their money and personal effects were highly subject to theft? Or as the premiss that these facts are a reason why innkeepers should be held liable in that way?) I argue against the normative reading of premiss (4): and the worry then is that the conclusion of the argument is not warranted, for  the conclusions of arguments by analogy in law are—we argue—normative claims about how novel cases should be decided.




1  Adams v New Jersey Steamboat Company 151 NY 163 (1896).

2  See MP Golding, Legal Argument (Peterborough, ON: Broadview 2001 [1984]) 44ff, 97ff. Authors who discuss Adams include S Brewer, ‘Exemplary Reasoning: Semantics, Pragmatics, and the Rational Force of Legal Argument by Analogy’ (1996) 109 Harvard Law Review 923-1028; LL Weinreb, Legal Reason: The Use of Analogy in Legal Argument (Cambridge University Press 2005); RA Posner, ‘Reasoning by Analogy’ (2006) 91 Cornell Law Review 761-774; J Finnis, ‘Analogical Reasoning in Law’ in his Philosophy of Law: Collected Essays, Volume IV (Oxford University Press 2011); F Schauer, ‘Analogy in the Supreme Court: Lozman v City of Riviera Beach’ (2013) 425-6.


Luís Duarte d’Almeida, University of Edinburgh School of Law