The Weaker Natural Law Thesis

• Published date: 01 December 2023
• Author: Charles F. Capps
• Date: 01 December 2023
• DOI: http://doi.org/10.1111/raju.12394

© 2023 The Authors. Ratio Juris published by University of Bologna and John Wiley & Sons Ltd.

Ratio Juris. Vol. 36 No. 4 December (333–349)

The Weaker Natural Law Thesis

CHARLES F. CAPPS*

Abstract. Natural law theories affirm that it belongs to the nature of law to be apt to promote

the common good or do something similar. I defend a weak version of this thesis according to

which part of what constitutes something as a nondefective central case of a posited law is that

it is apt to promote the common good. Just as the rules of Pictionary require the drawing player

to design her drawing to reveal the word in play, the rules of a central case of a legal system

require lawmakers to design laws to promote the common good. Therefore, just as a Pictionary

drawing that is inapt to reveal the word in play is defective, a central case of a posited law that

is inapt to promote the common good is defective.

1. Introduction

Theorists have used the labels “legal positivism” and “natural law theory” to de-

scribe a variety of views. As I will use the terms, they refer to contrasting views about

the nature of law. Natural lawyers affirm that it belongs to the nature of law to be

apt to promote “the common good” (Aquinas1948, pt. I-II, q. 90, a. 2; Duke2016b,

492–502; Finnis2012, 951), provide “a rational standard for conduct” (Crowe2016, 91;

Murphy2003, 244), or perform some similar function with a positive moral valence.

Positivists deny that it belongs to the nature of law to be apt to do any such thing. For

convenience, I will refer to the claim that natural lawyers affirm and positivists deny

as the claim that it belongs to the nature of law to be apt to “do something like pro-

mote the common good.” When I say that a law is “apt” to do something, I mean that

the law is capable (in appropriate circumstances, such as when properly interpreted

and enforced) of doing it.

Following Mark C. Murphy(2006, 10–11), I will distinguish two ways in which

natural law theory could be true. First, it might belong to the nature of law to be apt

to do something like promote the common good in the way that it belongs to the

nature of triangles to have three sides. That is, perhaps:

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution

and reproduction in any medium, provided the original work is properly cited.

* For their helpful comments, I am grateful to Ratio Juris’s anonymous reviewers; to Greg Brown,

Anton Ford, Melina Garibovic, Matthias Haase, Brian Leiter, Anselm Mueller, Mark Murphy,

Michael Rabenberg, and Laurenz Ramsauer; and to the participants in the Practical Philosophy

Workshop at the University of Chicago, where I presented a draft of this paper.

Charles F. Capps

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Ratio Juris, Vol. 36, No. 4© 2023 The Authors. Ratio Juris published by University of Bologna and John Wiley & Sons Ltd.

Strong Natural Law Thesis. Where ϕ-ing is something like promoting the common

good, part of what constitutes something as a legal rule is that it is apt to ϕ.

Second, it might belong to the nature of law to be apt to do something like promote

the common good in the way that it belongs to the nature of ducks to have an apti-

tude for swimming. That is, perhaps:

Weak Natural Law Thesis. Where ϕ-ing is something like promoting the common

good, part of what constitutes something as a nondefective legal rule is that it is

apt to ϕ.

The Weak Natural Law Thesis is not the natural lawyer’s only alternative to the

Strong Natural Law Thesis, however. For example, it might belong to the nature of

law to be apt to do something like promote the common good in the way that it be-

longs to the nature of criminal law to feature mens rea requirements. Laws making

it an offense to park in certain places at certain times typically feature no mens rea

requirements. Such laws may be called “criminal laws,” and they need not be defec-

tive. But they are borderline or peripheral cases of criminal laws in that they count

as “criminal laws” only in virtue of their relationship to central cases of criminal

laws, which do feature mens rea requirements (on the distinction between central

and peripheral cases, see Crowe2019, 149; Langlinais and Leiter2013, 682). Perhaps

part of what constitutes something as a central case of a legal rule is that it is apt to

do something like promote the common good (see, e.g., Finnis1980, 3–22, 276–81).

Or, it might belong to the nature of law to be apt to do something like promote

the common good in the way that it belongs to the nature of human action to be

reasoned. Involuntary human behaviors such as reflexes are human actions in the

sense that they are actions of a human. They are not mere peripheral or borderline

cases of actions of a human, and they need not be defective. Nonetheless, part of

what differentiates humans from other animals is the capacity for a specific kind

of action, namely, reasoned action. Thus, part of what constitutes something as

a specifically human action is that it is reasoned. Perhaps part of what constitutes

something as a specifically legal rule is that it is apt to do something like promote

the common good.

Finally, one might combine some or all of these ways of weakening the Strong

Natural Law Thesis. Combining them all produces what I will call the

Weaker Natural Law Thesis. Where ϕ-ing is something like promoting the common

good, part of what constitutes something as a nondefective central case of a spe-

cifically legal rule is that it is apt to ϕ.

Each of the three modifications to the Strong Natural Law Thesis that the Weaker

Natural Law Thesis incorporates weakens the Weaker Natural Law Thesis in the

sense that each narrows the range of legal rules that the Weaker Natural Law Thesis

claims are apt to do something like promote the common good. True, “nondefective”

would be redundant if central cases were necessarily nondefective, as some (e.g.,

Ehrenberg2016, 72–3; Gardner2007, 3) assume. But the notion of central cases intro-

duced above allows for defective central cases. For example, an off-key tryout for a

singing role in a musical is a defective central case of an audition—indeed, because it