In this concise and engaging lesson, part of the Legal Fundamentals Explained (LFE) series, Pedro Moniz Lopes (University of Lisbon) introduces the concept of analogy in law, explaining how analogical reasoning operates and why it plays a central role in legal interpretation and argumentation. He highlights the fact that analogy is a widely discussed and contested concept in legal theory and briefly outlines its main uses in legal reasoning.
Below, you can find the full transcription corresponding to this video lesson*.
Pedro Moniz Lopes
Hi. So, I’m back. If you have listened to me talking about the application of logic to law, or if you have not, I’m here for the first time. My name is Pedro Moniz. I’m a professor of legal philosophy at the University of Lisbon.
This time around, I’ll be talking to you about analogy. Analogy is a very contested concept and much discussed within legal theory. There are many theories about it. There are also many presuppositions that need to be expounded upon to better talk about analogy. But my purpose here is very moderate, since I have 10 minutes to talk to you about analogy. I will basically outline the uses one can make of analogy in general reasoning and particularly in legal reasoning.
Because you have analogy in general, you have analogy in fact-finding, legal analogy, historical analogy, political analogy, scientific analogy, and whatnot. But in legal reasoning, we have legal analogy. So I’ll just briefly outline the uses one can make, and sort of clarify the conceptual apparatus that we can make sense of when talking about analogy.
Specifically, I wish to structure the inferential steps of analogy. Of course, this is a specific theory of analogy—the inferential theory of analogy. There are many interesting papers written on this, particularly one by Damiano Canale and Giovanni Tuzet, called Analogy: An Inferential Approach—something like that. You can easily find it on the internet. It was published in Ratio Juris, I think in 2011.
Starting off with the uses of analogy—what are the uses of analogy? Analogy in general is not only used for problem-solving. Analogies are often used in explanations, where we use a source analog to provide for the understanding of a target phenomenon. This is very important to start with a general approach.
So, in analogy, you have a source that provides you with a certain piece of knowledge, and you have a target, which is something that you know something about, but there’s another thing that you want to know about. You always know something about the target—otherwise, you are not analogizing.
For instance, ancient people knew that metal was hot, and they wanted to know whether another sort of substance was able to be hot or not. They knew that substance was comprised of a certain matter, but they did not know whether it had the property to heat. Striking an analogy means transferring the knowledge from the source—in which you know that there’s a certain matter and the property of heating—to the target, which we know has a certain matter, which might or might not be sufficiently similar to the former source. And you want to know, according to valid and sound reasoning patterns, whether it heats as well or not.
You can use it in many cases, and it was actually the basis for human evolution. We evolved because we analogized. Whenever human beings were faced with dangers, they would strike an analogy between wild animals or threats and other types of targets of which they did not know whether they would be dangerous or not. And the soundness of those analogies allowed us to survive and be where we are today.
So, it’s important to know that both in general analogy and in legal analogy, there’s a specific goal. You can analogize to fill in the gap of a legal system. You can analogize to make a political argument. You can analogize to explain a causal process—for instance, in a trial regarding whether a certain substance was the cause of a certain event or not. There are many things you can do with analogies with different ends. And it’s very important to know that those ends are of paramount importance to analogy, because analogies change depending on whether those ends are in place.
In legal analogy, what usually is the case is that we want to analogize or differentiate between classes of cases. I would say we have four scenarios, and I’ll be using particulars P and Q—usually the variables for logic.
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Scenario one: Particular P is a member of category X, and particular Q is a member of the same category X, but we conclude that they should, all things considered, be members of different categories. So we are disanalogizing.
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Scenario two: Particular P is a member of category X, and particular Q is a member of category Y, when they should, all things considered, be members of the same category. So we are analogizing.
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Scenario three: Particular P is not a member of any category, and particular Q is a member of category X, when they should, all things considered, be members of distinct categories X and Y. Again, we are disanalogizing or differentiating.
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Scenario four: Particular P is not a member of any category, and particular Q is a member of category X, when they should, all things considered, be members of the same category.
This is just to say that legal analogy need not necessarily be connected with legal gaps. We can use analogical reasoning—or disanalogical reasoning—to differentiate between legal cases that are put together within the same legal regime, when, all things considered, they should have different outcomes.
I told you that I was going to outline a brief conceptual scheme or clarify the conceptual apparatus of analogy. I only have time to cover two or three terms that I think are very important to analogy.
The first is a category or class. A class or category—I’ll be using them interchangeably—is a collection of sets that can be clearly defined by a property that all its members share or are represented as sharing, whether you have the logical or psychological approach. In the strictest sense, a category is the set of objects that are considered equivalent. Equivalent is a logical concept that can be roughly translated into equal. So, analogy focuses on whether, all things considered, two particulars ought to have equivalent legal treatment.
Equivalence or equality is different from the property of similarity, or the relation of similarity. Similarity is a relation between two or more particular objects when they are perceived as sharing one or more properties. When we say that A and B are similar, we are not necessarily analogizing between them. They may be similar, but not similar enough to deserve equal, equivalent, or analogous legal treatment.
This is what I wanted to highlight—the difference between similarity that exists in the real world, that can be asserted between a comparison of particulars A and B, and analogy, which is instituted as some sort of equality that does not, as a normative concept, exist in the real world, but is set up, or instituted, or established by someone—by the one who is comparing, and who has adopted as a criterion for the comparison a certain meta-factor that will preside over the comparison.
So equality—and analogy—has to do with some sort of tunnel vision that disregards the similar properties and focuses on those properties which are deemed relevant for equivalent treatment.
How can we conceptualize analogy—or the argument from analogy? The argument from analogy, as I said before, is the process of inferring that a property or conclusion Q is to be predicated of a particular situation or object T (which is a target), from the fact that T shares a property or set of properties P with another situation or object S (which is a source) that has the property Q.
The set of common properties P is the similarity between the source and the target, and the conclusion property Q is projected from the source into the target.
The concept that is probably most important in analogical reasoning is the concept of relevance. Relevance is the predicate of a property of a particular. A certain particular has a certain property that is predicated as relevant when it is relevant according to a certain standard of relevance.
For instance, the fact that something is inflammable may be relevant for scientific analogies. The fact that it is conservative may be relevant for political analogies. In legal analogies, the concept of relevance is very tricky, because it has to do with the concept of ratio. The underlying reason or function of the law, which is highly disputed whether it really exists.
Irrespective of that, the structure of the analogical argument is the conjunction of three logical steps that were mentioned in the initial class regarding what one can get from logic in the law:
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Abduction of a relevant property,
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Induction, and
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Deduction.
So when setting up an analogy in general—and a legal analogy in particular—we are both aiming at inferential discovery and at a form of inferential justification.
How do we analogize? We start by having a certain target of which we want to know whether a certain legal treatment is deemed valid. It is not expressly foreseen in the legal system whether situation A leads to a permission of a certain action, or to a certain action being forbidden.
But we know that Q, which has some level of similarity with A, is regulated as being forbidden. So what we come up with—and this is the tricky part of circumventing the ratio legis and having the best legal explanation—is the abduction.
We abduct that the best possible explanation, for instance, for vehicles not being allowed in the park is the protection of the environment. That means that if an automobile is forbidden to enter the park, then a motorcycle, provided it pollutes as well, will also fall under the best explanation.
We get that theory as a justification for the source. Then we induct that all polluting devices are liable to go against the best explanation of the prohibition of automobiles entering the park. Therefore, motorcycles and, say, tractors and other types of combustion-driven vehicles are also part of polluting vehicles. So those deserve the same treatment.
And then we deduct—the target is a specific particular kind of thing that is part of the class that was inducted. We deduct that a moped—a motorcycle—is a type of polluting vehicle.
So basically, to finalize, we have the conjunction of:
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The abduction: the best possible explanation for automobiles being forbidden to enter the park is the protection of the environment;
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The induction: applying that best possible explanation to all kinds of polluting vehicles;
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And the deduction: this specific motorcycle is a polluting vehicle.
The legal treatment from the automobile is projected into the gap of regulation regarding the motorcycle.
So this is the basic outline of the analogical argument. I hope you enjoyed it. Thank you very much.
(*some minor grammatical and changes have been introduced in order to make the reading more fluid, but in no way altering the content or the format of each speaker’s interventions).
The LFE video series is powered by the EU Horizon Twinning project “Advancing Cooperation on The Foundations of Law – ALF” (project no. 101079177). This project is financed by the European Union.
