The Potential of Abductive Legal Reasoning

• DOI: http://doi.org/10.1111/raju.12268
• Published date: 01 March 2020
• Date: 01 March 2020
• Author: Bjarte Askeland

© 2020 The Authors. Ratio Juris published by University of Bologna and John Wiley & Sons Ltd

Ratio Juris. Vol. 33 No. 1 March 2020 (66–81)

The Potential of Abductive

Legal Reasoning

BJARTE ASKELAND

Abstract. The article describes the potential of abductive legal reasoning as a means of system-

atically exploring the role of inferences within legal reasoning. Starting out from the structures

of abduction as originally presented by Peirce in his four-horsemen example, the author points

to the fact that Peirce actually employed a hypothesis that targeted an institutional fact. Hence

the abductive inference has a great potential for categorising new phenomena under norms, yet

it is undertheorised within the field of law as compared to other fields of science. The article

presents the idea of comparison in the frame of “double abduction” as an important feature of

legal reasoning.

1. Introduction

Induction and deduction are two types of inference that are well known to most

scholars in most areas of science. The type of inference that is referred to as abduction

is more obscure to scholars. Abduction is a kind of inference that combines the per-

ceiver’s imagination, association, and intuition. The American philosopher Charles

Sanders Peirce launched in 1878 the theory of abduction as an integral part of his

programme of pragmatism (Peirce 1992, 186–88). Peirce’s original idea, crudely ex-

plained, focused on the fact that the human mind makes inferences based on in-

tuitions and associations, combining the observation of a new phenomenon with

already internalised background knowledge. In a later work that developed the idea

further, Peirce added that the inference that explains the new phenomenon then

comes to the perceiver “like a flash” (Peirce 1998, 227).

Peirce’s idea has been developed by later scholars into a theory of “inference to

the best explanation” (IBE) (Harman 1965). This has in some contexts been referred

to as a “strong” form of abduction, putting weight on the explanatory features of the

inference, whereas Peirce’s original idea of abduction or hypothesis has been named

a “weak” form of abduction, putting weight on the creative side of abduction (e.g.,

Amaya 2015, 203ff.). The two variations or “species” of abduction have been prob-

lematised in many publications (Abimbola 2001; Schum 2001).

In the weak form of abduction, the perceiver merely infers one explanation when

observing a new phenomenon.

Example. Anne observes her two friends Mike and Harry are laughing together in

the street (new phenomenon). She knows beforehand that the two of them have had

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Ratio Juris, Vol. 33, No. 1 © 2020 The Authors. Ratio Juris published by University of Bologna and John Wiley & Sons Ltd

The Potential of Abductive Legal Reasoning

a severe row. Anne infers that Mike and Harry have become friends again. (This in-

ference is the weak form of abduction.)1

In the strong form of abduction, the IBE theory renders both an initial selection of

several explanations and additionally a scheme for choosing the best of these expla-

nations (Iranzo 2007). Hence, abductive reasoning, in its developed form, offers the

best explanation available based on the perceiver’s background knowledge and new

information gathered.

The intellectual operations explained above have many commonalities with solv-

ing legal questions. Yet the subject of abductive reasoning within law is scarcely in-

vestigated. In this article I will explore the possible potential that abductive reasoning

holds within law and legal reasoning.

2. Abduction in Legal Reasoning

2.1. Introduction

Being a third type of inference, in addition to the more well-known induction and de-

duction, it is remarkable that abduction, or abductive reasoning, has not been explored

any further to achieve cognition within the field of legal method, adjudication, and

legal dogmatic works. This is odd, taking into consideration that it is a fact that ab-

ductive reasoning during the last decades has drawn attention in many other fields

of science. Discussion has been published extensively within the fields of philosophy,

medicine, and psychology, as well as the special debates concerning the phenomenon

of artificial intelligence (AI) (Magnani 2010; Park 2017). There have, however, not

been corresponding efforts within the field of law. An expressed opinion is also that

abductive reasoning so far has by no means reached its potential within social sci-

ences more generally (Thagard 2010).

Accordingly, in the following, the focus will fall on a special field of social science:

The potential of abduction within legal reasoning will be elaborated. Adapting abduction

to law may be seen as partly a quest for cognition in the field of adjudication and the

legal dogmatic discipline, and partly a contribution to the epistemology of solving

legal questions. An extremely thrilling thought in this respect is that, given that pat-

terns of abduction may be traced in various jurisdictions, in various legal cultures,

and on various levels of supranationality, the perspectives of abductive reasoning

may provide for new insights common to stakeholders throughout the European com-

munity of lawyers and beyond. Among stakeholders in this context one may count

legal philosophers, legal researchers, judges, and all kinds of jurists working in the

field of law.

As for the field of law, abductive reasoning has so far mainly been elaborated with

regard to evidence questions. This is only natural, since abduction, both in its original

(Peircean) form and in later versions, has been perceived as a means of finding out

what exists in the world. Thus, Amaya (2015, 503) holds that scholars of law have

mainly perceived inference to the best explanation as a “mechanism of discovery.”

An example is also Douglas Walton’s (2005) book, Abductive Reasoning, of which a

greater part is dedicated to evidence theory within the field of law. It seems, however,

1 The example is a variation of an example borrowed from Douven 2017.