Thucydides’ History of the Peloponnesian War is indeed a “possession for all time”. In a famous passage, the historian quotes the Athenians as saying that states are motivated by “fear, honour, and interest.” Any student of International Relations theory will readily recognize fear (security) and interest (economic power or advantage) as drivers of state behaviour. Honour appears at best as an afterthought in the most IR theories, if It features at all.
Richard Ned Lebow has argued that contrary to standard IR theories, such as Realism, states much more often resort to war out of “spiritual” (non-material) motives, including esteem, revenge, and honour. Interestingly, other interpreters of Thucydides’ work believe that he sees non-material motivations, such as honor, shame, vengeance and desire for liberty, as exerting much greater influence on the behaviour of states than the standard Realpolitik interpretation suggests. This is not the place to assess whether the empirical evidence sufficiently supports Lebow, or whether an alternative, non-realist interpretation of the History of the Peloponnesian War is defensible.
Rather, it is worth emphasizing that non-material motivations can have great strategic utility, including in the pursuit of material objectives, such as security and economic power. “Honour” and the implicit commitment to defend it can be a powerful signalling device as to a state’s willingness to incur material costs in pursuit of non-material goals. As such, non-material motivations have strategic effects. Honour effectively allows a state to make implicit promises and threats, whether a promise to defend allies or a threat to retaliate against an antagonist. “Shame” can have a very similar effects in terms of pre-committing to a course of action without having to explicitly commit to it. Ambiguity also has strategic effects.
Similarly, “vengeance” can be interpreted as pursing (or committing to) a retaliatory policy and commitment to strike back against an antagonist no matter what. Last but not least, the “desire for liberty” signals a commitment to the defense of immaterial objectives, making it difficult for an antagonist to calibrate policies in terms of material costs and benefits, as material and immaterial values are incommensurable. In extremis, this threatens to render politically (!) ineffective or less effective an antagonist’s deterrence and retaliatory policies. As the old adage goes, it is impossible to deter a suicidal terrorist. Calibrating the costs and benefits of policies in pursuit of a political objective, as opposed to total war and surrender, is made impossible. If credible, this can function as a powerful signalling device with outsized strategic effects.
The effectiveness of pursuing or being seen as pursuing non-material goals relies on their credibility. Signalling is only effective if it is credible, and this often requires the signaller to incur tangible costs. A public commitment to non-material values function as a signalling device. But it sends a message all the same. This is not to suggest that it is the strategic effects of non-material motivations that leads states to deploy them. Actually, the better able a state is to convince an antagonist that the these motivations are genuine, the greater their strategic effect will be. In this sense, they can enhance the strategic position of the state pursing non-material goals in view of more material goals, such as security and material gain. Again, much depends on the credibility of such a motivations in the eyes of the antagonist. But if credible, they signal a high tolerance for material costs. And this can be very useful, strategically.
War is the continuation of politics by other means. And strategy, as opposed to grand strategy, is the the process by which political purpose is translated into military action (Andrew Wilson, Naval War College). In this sense, strategy is here defined as strategic interaction rather than strategy, grand strategy or military strategy. Non-material motivations can strengthen a state's position in the context of strategic interaction with another state - at the very least in terms of signaling a potential nonchalance in terms of material costs. They are therefore equally political and strategic as well as instrumental in the pursuit of material goals, such as security and economic power. Thucydides was onto something important. And “honour” in the trinity of “fear, honour, and interest” is much, much more than a mere afterthought, as purely Realist interpretations of the History of the Peloponnesian have it.