Deterrence is a common strategy to try to dissuade someone from doing something you do not want them to do. This may be anything from speeding fines to surveillance cameras to deter theft to military readiness to deter aggressors from attacking a country.

But Frowe, who is a professor of philosophy at Stockholm University and a Wallenberg Scholar, believes that although deterrence plays a central role in domestic and international politics, there has not been enough research in the ethical aspects of deterrence mechanisms.

“Intuitively, people may think that deterrence is obviously OK – that of course I may install a security camera to prevent my house being burgled. But deterrence may cause or risk harm to other people because you want to protect yourself. For instance, will your neighbor run a greater risk of being burgled if you install surveillance cameras? These issues have not been properly discussed,” she says.

To date, discussions and formulation of theories of deterrence have centered on criminal law and nuclear deterrence. As a Wallenberg Scholar, Frowe will be adopting a broader approach, giving a broad account of the ethics of deterrence that can form the basis for discussions of specific applications.

“We need to gain a better understanding of the fundamental ethical principles of deterrence so we can make moral evaluations of different methods of deterrence and decide whether or not they are legitimate,” she explains.

I like to challenge the received wisdom on topics and try to understand where those views come from, what supports them, and whether they are plausible.

Funded by Knut and Alice Wallenberg Foundation, Frowe has spent the past few years building a research center at Stockholm University: the Stockholm Centre for the Ethics of War and Peace. As we speak she is finishing a book on the duty to rescue, and is about to recruit a PhD student and a postdoc to explore specific aspects of deterrence and related issues.

Scrutinizing defensive alliances

One type of deterrence that interests Frowe is collective defense agreements between countries. Their purpose is to deter enemies from attacking by threatening that an attack against one alliance member will cause all members to respond. But alliances of this kind might also increase the risk of non-member states being attacked, and reduce the chances of others coming to their aid.

This is illustrated by Russia’s full-scale invasion of Ukraine in 2022, explains Frowe. NATO members said they very much wanted to assist Ukraine’s defensive war, but claimed they were unable to do so: if Russia were to shoot down a NATO aircraft, the war would escalate dramatically.

“I’m not saying it’s always wrong to form or join these alliances – it’s probably permissible sometimes. But it is not as self-evidently morally permissible as we might think. This is something that governments should think about when they are considering defense alliances and other forms of deterrence.”

War as a deterrent

Deterrence is also sometimes used as a motive for military force. One example is the UK air strikes against the Houthi rebels in Yemen, which aimed to prevent a broader escalation of the Middle East conflict. Frowe’s research will include examining whether deterrence can be a just cause for war. Key issues are how we judge the success of deterrence –which depends on counterfactual claims on what would have happened otherwise – when it is permissible to harm some people in order to deter others from acting, and whether the harm caused to innocent people is proportionate.

“My view is that when you try to justify deterrence, you must primarily rely on the effects of harms to people who are responsible for the threat you are trying to deter – those who are legitimate targets,” she says. “If you need to rely on the harm to an entire population as part of the effectiveness of your deterrence, then it’s much less likely to be justified.”

Unpredictable results

One of the factors determining whether or not a deterrent action is legitimate is how likely it is to succeed. This can be very difficult to determine – many factors are weighed up when a state is deciding whether or not to start a war, for example.

“In practice it may be that deterrence should not be used because it is impossible to say how effective it will be.”

Frowe points out that the efficacy of deterrence largely depends on what people are driven by. It may be easier to deter someone who is making a calculated attempt to expand their territory, but harder to dissuade someone motivated by ideological convictions.

“I want to explore these variations and challenge the fairly unreflective assumption that deterrence is a just cause, as often expressed in public and political debate,” she says.

Text Sara Nilsson
Translation Maxwell Arding
Photo Magnus Bergström