Death of Paradox: The Killer Logic Beneath the Standards of Proof

65 Pages Posted: 17 Jan 2012 Last revised: 24 Jul 2012

Kevin M. Clermont

Cornell Law School

Date Written: February 11, 2012


The prevailing but contested view of proof standards is that factfinders should determine facts by probabilistic reasoning. Given imperfect evidence, they first should ask themselves what they think the chances are that the burdened party would be right were the truth to become known, and they then should compare those chances to the applicable standard of proof.

I contend that for understanding the standards of proof, the modern versions of logic — in particular, fuzzy logic and belief functions — work better than classical probability. This modern logic suggests that factfinders first assess evidence of an imprecisely perceived and described reality to form a fuzzy degree of belief in a fact’s existence, and they then apply the standard of proof by comparing their belief in a fact’s existence to their belief in its negation.

This understanding nicely explains how the standard of proof actually works in the law world. While conforming more closely to what we know of people’s cognition, the new understanding captures better how the law formulates and manipulates the standards and it also gives a superior mental image of the factfinders’ task. One virtue of this conceptualization is that it is not a radical reconception. Another virtue is that it nevertheless manages to resolve some stubborn problems of proof, including the infamous conjunction paradox.

Keywords: civil procedure, evidence, standard of proof

JEL Classification: K41

Suggested Citation

Clermont, Kevin M., Death of Paradox: The Killer Logic Beneath the Standards of Proof (February 11, 2012). Notre Dame Law Review, Vol. 88, 2012; Cornell Legal Studies Research Paper No. 12-6. Available at SSRN: or

Kevin M. Clermont (Contact Author)

Cornell Law School ( email )

Myron Taylor Hall
Ithaca, NY 14853
United States
607-255-5189 (Phone)
607-255-7193 (Fax)

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