No paradox here? Improving theory and testing of the nuclear stability–instability paradox with synthetic counterfactuals

AuthorBenjamin E Goldsmith,Francesco Bailo
DOI10.1177/00223433211018501
Date01 November 2021
Published date01 November 2021
Subject MatterRegular Articles
No paradox here? Improving theory and
testing of the nuclear stability–instability
paradox with synthetic counterfactuals
Francesco Bailo
School of Communication, University of Technology Sydney
Benjamin E Goldsmith
School of Politics & International Relations, Australian National University
Abstract
This article contributes to both the theoretical elaboration and empirical testing of the ‘stability–instability paradox’,
the proposition that while nuclear weapons deter nuclear war, they also increase conventional conflict among
nuclear-armed states. Some recent research has found support for the paradox, but quantitative studies tend to pool
all international dyads while qualitative and theoretical studies focus almost exclusively on the USA–USSR and
India–Pakistan dyads. This article argues that existing empirical tests lack clearly relevant counterfactual cases, and
are vulnerable to a number of inferential problems, including selection on the dependent variable, unintentionally
biased inference, and extrapolation from irrelevant cases. The limited evidentiary base coincides with a lack of
consideration of the theoretical conditions under which the paradox might apply. To address these issues this article
theorizes some scope conditions for the paradox. It then applies synthetic control, a quantitative method for valid
comparison when appropriate counterfactual cases are lacking, to model international conflict between India–
Pakistan, China–India, and North Korea–USA, before and after nuclearization. The article finds only limited
support for the paradox when considered as a general theory, or within the theorized scope conditions based on
the balance of resolve and power within each dyad.
Keywords
interstate conflict, nuclear deterrence, nuclear weapons, synthetic control method
Motivation
This article advances theoretical development and testing
of the ‘stability–instability paradox’, a longstanding aspect
of nuclear deterrence. The theory expects that while
nuclear weapons deter nuclear war, they also lead
nuclear-armed states to increase conventional military
conflict with each other. ‘[T]he greater the stability of the
“strategic” balance of terror, the lower the stability of the
overall balance at its lower levels of violence’ (Snyder,
1969: 123; see also Jervis, 1984: 31–34; Zagare, 1992).
A recent review finds a cumulation of evidence of ‘limited
war’ among nuclear states (Geller, 2017: 12). But our
findings suggest the evidence is far from conclusive, even
considering scope conditions that sharpen the theory.
Important formal-theoretical and quantitative research
appears to supportthe paradox (Powell, 2015; Rauchhaus,
2009). Other recent work on nuclear security tends to
accept it as an established fact, incorporating the paradox
as a foundation for related empirical or theoretical inves-
tigation (Kydd, 2019; Watterson, 2017). However, at
least one quantitative study (Bell & Miller, 2015) does
not find support, and some qualitative studies of India
and Pakistan deliver equivocal assessments (Ganguly &
Hagerty, 2006; Kapur, 2005, 2007; Narang, 2010).
Corresponding author:
ben.goldsmith@anu.edu.au
Journal of Peace Research
2021, Vol. 58(6) 1178–1193
ªThe Author(s) 2021
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/00223433211018501
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We argue that studies of the stability–instability par-
adox (hereafter SIP) using traditional quantitative and
qualitative methods face significant challenges for valid
inference. Gartzke & Kroenig (2017: 1853) call for
‘[m]ore precise theory’ and ‘improved methods of infer-
ence’ in the study of nuclear security issues. In this article
we clarify theoretical scope conditions for SIP, reflected
in two hypotheses based on Powell’s (2015) formal
model, and use a newer method across three appropriate
cases. Only one of our cases fits the general expectation.
There are several challenging aspects of applying syn-
thetic control to interstate conflict data, but it has dis-
tinct advantages and adds essential new evidence to the
debate.
We first discuss the existing literature on SIP, focusing
on barriers to valid inference, and address theoretical
foundations. We then describe research design, present
empirical analysis for three cases for which we have suf-
ficient data, and conclude.
Barriers to inference
Empirical tests of SIP are vulnerable to several inferential
problems. A concern for qualitative studies is selection
on the dependent variable (Geddes, 1990). Two dyadic
cases dominate the literature: Soviet Union–United
States and India–Pakistan. It is hard to imagine these
cases were not chosen because they appear to confirm
the theory. After the USSR acquired nuclear weapons
in 1949, the Cold War escalated. After Pakistan became
a nuclear power in 1990, tensions over Kashmir
increased; the 1999 Kargil War erupted after nuclear
tests in 1998. These cases have contributed to the theo-
ry’s development and survival (Cohen, 2013; Montgom-
ery & Edelman, 2015), but selection on the dependent
variable can lead to misplaced inference and inattention
to alternative explanations.
Qualitative studies may also suffer from unintention-
ally biased interpretation. Motivations behind specific
military-security decisions – notoriously difficult to con-
firm – are key pieces of evidence. If interpretation is
consistent with expectations, this can lead to false-
positive findings, a type-I inferential error.
Analysts of India–Pakistan relations debate whether
the nuclear balance causes Indian restraint and Pakistani
belligerence. Evidence may be emphasized because it
appears to improve the explanatory power of a preferred
variable, despite other plausible explanations. A case in
point is two prominent authors’ different inferences
about the role of international opinion in India’s
restraint in the Kargil War.
Kapur (2008: 77) writes:
V.P. Malik, Indian Army chief of staff during the Kargil
operation, explains that the Indians avoided crossing the
Line of Control mainly out of concern for world opin-
ion: ‘The political leaders felt that India needed to make
its case and get international support’ for its position in
the conflict. The Indian g overnment believed that it
could best do so by exercising restraint even in the face
of clear Pakistani provocations.
But Ganguly (2008: 59) argues:
One seemingly plausible explanation for India’s restraint
might have been the perceived need to court interna-
tional public opinion in the aftermath of the nuclear
tests. This argument does not withstand scrutiny, how-
ever. Given the resentful public mood within the coun-
try, an upcoming general election, and the existence of a
regime that had few qualms about the use of force to
resolve disputes, the inhibitions of global public opinion
could not have served as a powerful barrier to the expan-
sion of the conflict. [ ...] Consequently, even in the
absence of incontrovertible public statements, through
a process of inference and attribution, one can make a
cogent argument that the principal source of Indian
restraint was Pakistan’s overt possession of a nuclear
arsenal. Indian policymakers, cognizant of this new real-
ity, were compelled to exercise suitable restraint for fear
of escalation to the nuclear level.
Adjudication between such competing assertions does
not seem possible given the available evidence. As Leng
(2006: 116) writes, ‘[t]here is no solid evidence’ to sup-
port particular claims about Indian restraint, only ‘attri-
butional distortion’.
Similarly, qualitative inference may be attempted from
evidence that does not logically warrant it. Kapur (2008:
74–75) appears to treat Pakistani Prime Minister Benazir
Bhutto’sclaims in this way, writing:‘Pakistani leaders have
openly acknowledged nuclear weapons’ emboldening
effects. Benazir Bhutto, who servedher first term as Pakis-
tani prime minister from 1988 to 1990, stated [ ...]
“Islamabad saw its capability as a deterrence to any future
war with India,” [ ...] because “a conventional war could
turn nuclear”’. Logically, acknowledging a nuclear deter-
rent does not justify inference of ‘emboldening effects’.
Since she was not in power during major instances of
emboldenedPakistani behavior such as the 1987initiation
of the Kashmir insurgency or the Kargil War, causalinfer-
ence from her statements is further open to question.
Although the evidence seems indeterminate, qualita-
tive empirical support for the paradox hinges on just
Bailo & Goldsmith 1179

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