Generalizations and Reference Classes

Philosophical Foundations of Evidence Law (Oxford University Press, Christian Dahlman, Alex Stein & Giovanni Tuzet eds.), Forthcoming

22 Pages Posted: 13 Oct 2020

Date Written: October 2020


Legal scholarship exploring the nature of evidence and the process of juridical proof has had a complex relationship with formal modeling. An example of this complex relationship concerns attempts by scholars to use mathematical models to quantify the probative value of evidence in order to study decision-making from that perspective. As with earlier attempts to apply probability theory to juridical proof, this scholarship is interesting, instructive, and insightful. However, it also suffers from a deep conceptual problem that makes ambiguous the lessons that can be drawn from it — the problem of reference classes.

In this chapter, we examine the implications of the reference-class problem for attempts to model the probative value of items of evidence. This chapter makes three contributions. First, and most importantly, it is a further demonstration of the problematic relationship between algorithmic tools and aspects of legal decision-making. Second, it points out serious pitfalls to be avoided for analytical or empirical studies of juridical proof. Third, it indicates when algorithmic tools may be more or less useful in the evidentiary process. At the highest level of generality, this chapter is another demonstration of the very complex set of relationships involving human knowledge and rationality, on the one hand, and attempts to reduce either to a set of formal concepts, on the other.

Keywords: evidence, statistical evidence, probative value, likelihood ratio, reference-class problem

Suggested Citation

Pardo, Michael S. and Allen, Ronald J., Generalizations and Reference Classes (October 2020). Philosophical Foundations of Evidence Law (Oxford University Press, Christian Dahlman, Alex Stein & Giovanni Tuzet eds.), Forthcoming, Available at SSRN: or

Michael S. Pardo (Contact Author)

Georgetown University Law Center ( email )

600 New Jersey Avenue, NW
Washington, DC 20001
United States


Ronald J. Allen

Northwestern University Pritzker School of Law ( email )

375 E. Chicago Ave
Chicago, IL 60611
United States
312-503-8372 (Phone)
312-503-2035 (Fax)

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