Nudging, fast and loose

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James Wilson, Senior Lecturer, Department of Philosophy, UCL

Thaler and Sunstein’s Nudge owes its wide success to its approachability and the apparent ease and cheapness of translating its recommendations into changes that could make a difference. Of course, it’s difficult to write a work that is approachable enough to be sold in airports, yet precise enough to be able to withstand the most demanding academic scrutiny. Commentators have found some difficulty in reconciling the different definitions that Thaler and Sunstein give of what counts as a nudge, and further difficulties in reconciling these definitions with their examples of nudges.

Mongin and Cozic (2017) argue that despite what Thaler and Sunstein may think, there are in fact three separate concepts of a nudge in the book:

(1) an intervention that interferes with the choice conditions minimally; (2) an intervention that uses rationality failures instrumentally; and (3) a welfare-promoting intervention that tries to reduce the negative effects of rationality failures.

They show convincingly that none of these different definitions are equivalent, and that few interventions will be nudges in all three senses. Their tentative conclusion is that it may be helpful to separate the three nudge concepts out and explore each in isolation.

A key question that arises from this analysis is what we want ‘nudge’ to do. Wittgenstein famously argued that a concept such as that of a game may be in good order, even if there is no one thing that all games have in common. (Philosophical Investigations, 66) Given the variety of the cases that Thaler and Sunstein have described as nudges, and the ways in which these cut across Mongin and Cozic’s three specifications of the concept, a Wittgensteinian family resemblances account may provide a better interpretation of Thaler and Sunstein’s use of the concept than attempting to transform their cursory attempts at definition into a tight set of necessary and sufficient conditions. In any case, given that the concept of a nudge has now spread far into the public sphere, it may be difficult to wrest control of the concept back and to separate it out into three neat boxes.

So why we should care whether an intervention is classed as a nudge rather than something else? Mongin and Cozic’s account does not give us an answer. In thinking through what their answer should be, it’s important to take account of the broader context. Nudge rose to prominence alongside and as part of Thaler and Sunstein’s espousal of libertarian paternalism. Libertarian paternalism is paternalistic in that it takes it to be legitimate for public or private planners to intervene in individuals’ lives in ways that “steer people’s choices in ways that will improve their lives”, but is libertarian because “choices are not blocked, fenced off, or significantly burdened” (2008, p.5). As Thaler and Sunstein put it, “if people want to smoke cigarettes, to eat a lot of candy, to choose an unsuitable health care plan, or to fail to save for retirement, libertarian paternalists will not force them to do otherwise—or even make things hard for them” (2008, p. 8).

Welfare state systems regularly go far beyond these limits in protecting the welfare of their citizens. Take smoking for example. The 181 states party to the UN Framework Convention on Tobacco Control commit themselves to “protect present and future generations from the devastating health, social, environmental and economic consequences of tobacco consumption”, by “legislative, executive, administrative and/or other measures”. These measures include increasing price and taxes on tobacco, ensuring protection from exposure to tobacco smoke, prominent health warnings of no less than 30% of the size of the packet, and comprehensively banning all forms of tobacco advertising, promotion and sponsorship. (, Articles 6–14)

The extent of these commitments is plainly incompatible with ensuring that any tobacco discouragement measures should not “even make things hard” for smokers. It is notable that the US, which provides the main locus for Thaler and Sunstein’s theorising, has not ratified the Framework Convention. It may be that libertarian paternalism owes what currency it has to the unusual way that US  citizens tend to think about the role of the state.

If libertarian paternalism gets the limits of state action wrong, and it is sometimes or even often appropriate for the state to “block, fence off, or significantly burden” choices to improve individuals’ welfare, then clearly nudges will be only one mechanism amongst many the state can legitimately use. Elsewhere, I have argued that a state that confined its attempts to improve individuals’ lives to what could be justified in libertarian paternalist terms would violate its citizens’ rights to health by failing to take proportionate steps to protect them from serious and avoidable threats to their wellbeing. (Wilson 2016) Even if you don’t agree with me on this point, I think it’s likely that you will agree that an intervention’s being a nudge is neither necessary nor sufficient for its being justifiable.

Mongin and Cozic seem to think that it is a virtue of their account that they, unlike the vast majority of those who have written on the topic, divorce the analysis of nudge from a wider analysis of libertarian paternalism. But shorn of any background commitment to libertarian paternalism, it’s not completely clear to me why it should matter from a public policy perspective whether an intervention is classed as a nudge, let alone which of the three nudge sub-concepts it falls under.

Read the article “Rethinking nudge: not one but three concepts” by Philippe Mongin and Mikael Cozic in the journal here


Richard Thaler and Cass R. Sunstein (2009). Nudge: Improving decisions about health, wealth and happiness. (London: Penguin)

Ludwig Wittgenstein (1953). Philosophical Investigations. (Oxford: Blackwell)

James Wilson (2016). “The right to public health.” Journal of Medical Ethics 42.6: 367-375.