Evidence-based policies, nudge theory and Nancy Cartwright: a search for causal principles ALEJANDRO HORTAL* Department of Languages, Literatures, and Cultures, University of North Carolina Greensboro, NC, USA Abstract: Nancy Cartwright argues that evidence-based policies should not only rely on randomized controlled trials (RCTs) to test their effectiveness – they should also use horizontal and vertical searches to find support factors and causal principles that help define how those policies work. This paper aims at analyzing Cartwright’s epistemology regarding evidence-based policies and their use of RCTs while applying her findings to current research involving nudges as behavioral public policy interventions. Holding a narrowly instrumental view of rationality, nudge theory tends to neglect other expressive components. Policymakers, in their quest for causal principles, should consider the expressive rationality of individuals in their research. This inclusion would not only increase the effectiveness of nudges, but also address some ethical issues related to people’s autonomy when targeted by these interventions. Introduction Since the publication of Nudge (Thaler & Sunstein, 2009), public policymakers have been using nudges as interventions based on behavioral insights to modify the behavior of citizens predictably by manipulating their choice environment. Governments and other institutions have created a multitude of nudge units that draw from this theory since its premise assumes the preservation of liberty (nudges do not coerce) while paternalistically it is capable of orienting behavior to the desired target (libertarian paternalism). According to Adam Oliver, nudges, as they focus upon internalities, are “the dominant framework in behavioral public policy to date” (2019, p. 147) * Correspondence to: Department of Languages, Literatures, and Cultures, University of North Carolina Greensboro, Moore Humanities Research Building, Office 1119, Greensboro, NC. USA. Email: a_hortal@uncg.edu Behavioural Public Policy, Page 1 of 20 © The Author(s), 2020. Published by Cambridge University Press doi:10.1017/bpp.2020.55 1 of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/bpp.2020.55 Downloaded from https://www.cambridge.org/core. IP address: 52.91.53.142, on 01 Jan 2021 at 16:13:27, subject to the Cambridge Core terms