Sources of legal indeterminacy

• DOI: https://doi.org/10.47348/SALJ/v138/i1a6
• Pages: 115-151
• Published date: 04 March 2021
• Date: 04 March 2021
• Citation: 2021S (1) SALJ 115
• Author: Du Plessis, Q.

115

SOURCES OF LEGAL INDETERMINACY

*

QUENTI N DU PLESSIS†

Johannesburg Bar

Traditional analyses charact erise or identi fy vagueness an d ambiguity as the sol e or

primary sou rces of legal indet erminacy. In this a rticle, I identif y and characte rise

various other sou rces of legal indetermina cy. In addition to the semantic indeter minacy

of vagueness and a mbiguity, philosophers of la nguage have iden tied conversa tional,

pragmatic, and con textual indete rminacy, each of whi ch is capable of g enerating a

‘hard case’ a s applied to the legal sp here. Nor is all legal in determina cy linguistic in

nature. Followin g Henry Prakken, I identify non -monotonicity, or the fact that legal

inferences a re defeasible, a s a nal source of lega l indetermin acy. Each source of lega l

indetermina cy thus identied includes ca se-law exampl es to aid in the discu ssion.

Legal i ndeterm inacy – s emantic s – vaguenes s – ambigu ity – interpretation

– context

‘Look for precis ion in each cla ss of thin gs just so f ar as the nat ure of the

subject adm its.’1

I IN T RODU CTI ON

Law is not like m athematics or physics. It does not cons ist of the application

of abstract pr inciples to concr ete scenar ios to yield un iquely true an swers.

Every legal s ystem has leg al oblig ations and r ights, t he precise content of

which is indeter min ate. Indeterm inate leg al norm s generate har d cases in

their penumbr a of application. The d istin guish ing featu re of hard ca ses

is that no deci sion procedure consider ing on ly the dictat es of law could

tell one what the outcome w ill be. To the extent th at certa in legal nor ms

generate har d cases, they po se an imme diate and obv ious chal lenge to the

rule of law. If we take the poi nt of the rule of l aw to be the guid ance of

legal subject s, then such norm s are a fai lure, since they c annot gu ide our

behaviour, since we ca nnot know what count s as a violat ion of them.

All leg al norms a re indeterminate to a g reater or lesser extent. No legal

norm is per fectly deter minat e. We can measure the ind etermi nacy of a

legal norm by t he relative size of the set of hard ca ses to the set of easy cases

that it could poss ibly generate. For in stance, s 10 of the Const itution of

the Republic of South Af rica, 1996 (‘the Con stitution’), which st ates that

‘[e]veryone has inherent d ignit y and the ri ght to have their d ignit y

* T his ar ticle is bas ed substan tial ly on ch 2 of my LLM di sserta tion which,

in tur n, owes much to ch 1 (‘Form s of legal i ndeterm inacy ’) of David Lan ius

Strategic Indeterminacy in the Law (2019). Many tha nks go to L anius for a llowi ng

me to stand on h is shoulder s. Than ks go al so to my superv isor, Profes sor Anton

Fagan, for i ncisive com ments dur ing the wr iting of the draf t. Any erro rs remai n

mine alone.

† BSocSc LLB LLM (Cape Town).

1 Arist otle Nicomachean Ethics (tr W D Ross) (1942) I iii 1094b.

https://doi.org/10.47348/SALJ/v138/i1a6

(2021) 138 SALJ 115

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116 (2021) 138 TH E SOUTH AFRICA N LAW JOURNAL

https://doi.org/10.47348/SALJ/v138/i1a6

respected and pr otected’,2 is ext remely indeter mina te,3 since the set of

hard case s that it could generate is arg uably larg er than the set of e asy case s

that it could gener ate.4

Thus underst ood, indeter minac y is a moda l notion.5 One conse quence

is that a lega l norm is actual ly indeterminat e only relative to some context.

Section 10 of the Constit ution is per fectly deter mina te as applied to

the context of a lega l subject purp orting t o stand in the r elationsh ip of

ownership to a nother legal subject. Thi s would be a clear case of a violat ion

of s 10. Similar ly, s 10 is perfectly deter mina te as applied to the cont ext

of a legal subject pu rport ing to sta nd in the relat ionship of ownersh ip to

a legal object. T his is a clea r case of non-violat ion of s 10. Even the most

indeterm inate leg al norms a re thus act ually d etermi nate when applied to

an appropriat e context.

The extent to which a leg al norm succeeds i n guiding t he behaviour of its

subjects wi ll depend on its indeterm inacy. Completely indeterm inate legal

norms fa il completely to g uide our behav iour since there is , ex hypothesi,

no context in which it is c lear whether they apply. Less indeterm inate legal

norms gu ide our behaviou r only relat ive to some context. If, re lative to

some context, an i ndeterminate le gal norm generate s an easy case, then t hat

norm wil l succeed in g uiding ou r behaviour. If, r elative to some contex t,

an indeter minate legal norm g enerates a hard case, then t hat norm will fa il

in guid ing our behav iour. Completely deter minate le gal norm s should,

ceteris pa ribus, succeed complet ely in guid ing our beh aviour.

One way to thin k about the dierence between law and m athematic s is

that, un like mathematics , the legal system does not v alidate the princ iple of

bivalence. In logic, t he principle of bivale nce states tha t every proposit ion

2 The Constitut ion, s 10.

3 Both Deek sha Bhana a nd Gerha rd Lubbe arg ue in eect th at dign ity is

multidi mensional in that it i ncorporates both ‘empower ment’ and the notion that

humans s hould not be tre ated as the mea ns to an end. S ee Deeksha Bh ana ‘The

law of contract a nd the Constitution’ (20 07) 124 SALJ 269 at 274; Gerhard Lubbe

‘Taking fu ndament al rig hts seriou sly: The Bi ll of Rig hts and its i mplicat ions

for the development of cont ract law’ (20 04) 121 SALJ 395 at 420–1. Dig nity,

according t o Lubbe (at 421), can pull in opp osite dir ections. Se e also Jan S mits

‘Private l aw and fund amenta l right s: A sceptica l view’ in Tom Barkhuy sen &

Siewert Linde nbergh (eds) Const itutionalisation o f Private La w (2006) 9 at 17 and

F D J Brand ‘The role of g ood fait h, equity a nd fair ness in t he South Af rican

law of contract : The inuence o f the common law a nd the Const itution’ (2009)

126 SALJ 71 at 86: ‘[D ignit y is] simply too vague to provi de a decisive an swer in

deciding cases.’

4 For this rea son, callin g these cases ‘penumbra l’ or ‘borderli ne’ is a misnomer

as applied to ex tremely indeterm inate leg al norm s.

5 Modal proposition s are proposit ions subject to e ither of the sentent ial

operators ‘ it is possible t hat’ or ‘it is ne cessar y that’ (as op posed to ‘it is a ctua lly

the case th at’). In the sense u sed here, to say that a proposition p i s indeter minat e

is equival ent to ‘it is pos sible that p cou ld generate a h ard case’.

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SOURCES OF LEGA L INDETERM INACY 117

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has one and onl y one truth va lue: true or fa lse. The set of al l propositions

would then be div ided equal ly between t wo mutual ly exclusive and

exhaust ive subsets: the set of a ll true pr opositions and t he set of all f alse

propositions. In l aw, juridical biva lence would entai l that ever y legal

proposition is either t rue or fal se, and not both, a nd not neither. Thus,

every person either is or i s not guilt y; every action either does or does not

constitute a del ict; and ever y agreement eit her is or is not un lawfu l.

Despite this be ing the layp erson’s view of the law, it is false. The re ason

is legal ind etermi nacy. This a rticle ai ms to identi fy, in a sort of ta xonomy

of legal indet ermi nacy, some of the most pert inent ways tha t juridica l

bivalence can fa il. I have al ready identi ed, on the most gener al level,

one way in which it can fa il: two mut uall y exclusive legal ut terances a re

not always mutua lly ex haustive of the leg al space. There a re several ways

in which thi s can happen, but mos t scholars focu s on just two: vaguenes s

and ambig uity.

In this a rticle, I propose a mod icat ion and extension of L anius’s

taxonomy of ways th at juridic al bivalence ca n fail.6 Accord ing to th is

classi catory scheme, vaguenes s and ambig uity ar e mere species amon gst

genera. I attem pt, furt her, to make the d iscussion of each sou rce of legal

indeterm inacy conc rete by discu ssing ca se law example s of each.

The article i s organ ised as follows . Part II is ded icated to an

exploration of sem antic indete rmin acy, which includes vag ueness and

ambigu ity. Vagueness can fu rther be d isting uished bet ween its sorit ical

and combinator ial ma nifest ations, and a mbigu ity between it s syntact ic,

lexical, a nd polysemous ma nifest ations. Par t III concerns conver sational

vagueness , which occurs when a n uttera nce borderline sa tises a

Gricean convers ational m axim , the most common ex ample of which is

generalit y. Part IV is concer ned with pra gmatic i ndeterm inacy, which

occurs when a propos ition that is sem antica lly deter minat e nonetheless

generates ind etermi nacy due to pra gmat ic consideration s surround ing the

utterance. Th is includes implicat ure indetermin acy, speech-act ambiguit y,

presupposition ind etermi nacy, and expl icature ind etermi nacy. Part V

looks at indeter minac y in context, w hich is concerned w ith the problem

of context-dete rmin ation.

Part VI cons iders a wholly d ierent source of leg al indeter min acy,

which is due not to two mut ually e xclusive legal ut terances not bei ng

mutual ly exhaust ive of the legal sp ace, but due rather to the fa ct that the

truth of one of a set of t wo mutual ly exhaus tive legal ut terances doe s not

guara ntee the fal sity of the ot her. Here, I focus on the non-monotonic ity

of legal rea soning, wh ich is to say that a ll lega l propositions a re, at least in

principle, defea sible. Part V II concludes the ar ticle.

6 S ee David La nius ‘Form s of indeter mina cy’ in hi s Strategic Indeterminacy in

the Law (2 019) 4– 61.

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