The relation between neutrality and the use of force is better to be kept within the law of armed conflict rather that the law on the use of force between States. This means that the right of self-defence cannot be the indispensable legal basis for the use of force between belligerents and neutrals. On the contrary it appears that neutral due diligence has been relied on as a basis to expand the scope of the right of self-defence. The latter is admissible as the basis for resort to force only in the case of resistance of a neutral State to repel belligerent violation of its territory or by a belligerent that fully complies with its duties under the law of neutrality.

Just as a debate about the fundamental nature of physical entities arose after Descartes, a similar issue arose after Newton. Like Descartes, but of course with very different epistemological and methodological considerations, Newton held that the most fundamental conserved quantity was “quantity of motion” or momentum. Leibniz opposed this, arguing instead for vis viva or “living force.” This controversy introduced two kinds of problems: 1) whether and how empirical proofs could be generated for metaphysical conceptions, and consequently 2) how to understand the relationship between metaphysics and experimental philosophy. These concerns were handled quite differently by two important philosophers: Gravesande and Du Châtelet. Their moves partly resolved older debates, but also partly reconfigured them into new questions we are still attempting to answer.

In this chapter, I analyze the connections that Hume draws between utility as a source of merit, the principle of humanity as that which elicits our approval of useful mental qualities and blame for pernicious ones, and the role of reason, both in determining usefulness and in reaching just evaluations of merit or demerit. I contrast this set of connections with another set of moral sentiments that have as their object the immediately agreeable or disagreeable qualities. I reconstruct the argument meant to establish the principle of humanity as the foundation of morality, in part with the aim of showing that the sentiment of humanity gains force through our collective participation in the common point of view from which we form a general standard of virtue.

Chapter 5 is mainly devoted to the interaction between waves and immersed bodies. In general, an immersed body may oscillate in six different modes, three translating modes (surge, sway, heave) and three rotating modes (roll, pitch, yaw). An oscillating body radiates waves, and an incident wave may induce a corresponding excitation force for each one of the six modes. When a body oscillates, it radiates waves. Such radiated waves and excitation forces are related by so-called reciprocity relationships. Such relations are derived not only for a single oscillating body but even for a group (or 'array') of immersed bodies. Axisymmeric bodies and two-dimensional bodies are discussed in separate sections of the chapter. Although most of this chapter discusses wave-body dynamics in the frequency domain, a final section treats an immersed body in the time domain.

Referring to a simple illustration, a verbal explanation is given by the essential, but perhaps paradoxical, statement that to absorb wave energy from a wave by means of an oscillating system, it is required that the system radiates a wave which interferes destructively with the incident wave. Then various mathematical relations are derived concerning the conditions for an oscillating body to remove energy from an incident wave. The mathematical conditions for wave-power absorption may be illustrated as a paraboloid-shaped 'island' on an infinite complex-plane 'ocean' surface. The top of this 'island' corresponds to maximum absorbed power. An additional matter is the optimum control of a wave-energy converter (WEC) body. Thus far, the WEC body's shape and oscillation mode have been taken into account, but not its physical size. The latter is an important parameter related to the cost of the WEC, when the Budal upper bound is explained and discussed. Another important phenomenon, related to the Keulegan–Carpenter number, is discussed, in relation to an example of a WEC body. In a final section of the chapter, a WEC body, oscillating in several modes of motion, is discussed.

This essay examines Simone Weil’s interpretation of the Iliad – found in her “The Iliad or the Poem of Force” – as a strongly critical meditation on the dehumanizing effects of force, violence, and war in human affairs.

Force itself is not as straightforward as it might at first appear. Stealth proved a communicative endeavour; Chapter 7 shows that force is too. What does force intend to communicate in the context of armed conservation and acquisitive politics? Who is the intended audience? What values underlie the actors’ moves? Pisteurs often use the idiom of vengeance to answer those questions, or that of why they pursue manhunts. But vengeance invites further exploration, too. It has often been thought of as a mode of law, a balancing mechanism. Vengeance, in the way in which pisteurs, hunters, and herders enact it, in contrast, is a means of communicating a claim to status. Who is not to be messed with? Who can be subjected to seizure or other insults? How does one respond if attacked? Recourse to vengeance is particularly valuable to people who do not have reliable access to institutional means of protection; it is a mode of denunciation, and a claim to sovereignty, oriented not towards control but towards liberty. Denunciation, like vengeance, is conversational – only in rare cases is it so definitive as to become a Parthian shot, and instead it often becomes a continuing cycle. Few are happy that denunciation is so prevalent, but many see their own denunciations as necessary. By denouncing, they claim an exception from violence that would demean but not include them, as well as from associated rules and norms, and as such it is a process of solidarity and claiming liberty.

Although forceful, militia-led conservation continues in north-eastern CAR, it has been joined and at times supplanted by rebellions, some led by former pisteurs who have turned their martial skills to this new end. Rebellious ways and intervention by outsiders have long histories in Central Africa, but the particular forms these practices have taken in the last 15 years are new. Among other changes, men consciously self-style as rebels, and there has been an enormous influx of the people I have elsewhere called the ‘good intentions crowd’ (international organisation officials, aid organisation employees, diplomats, and others who understand themselves as ‘external’ and altruistic and yet become central and interested participants in rebellion in post-Cold War Africa). This chapter shows how the new rebels relate to and transform the serious games around forceful acquisition and status that are the book’s main focus. This project provides an opportunity to sit with four adventurous men involved in these shifts around force, acquisition, and status over the last few decades. All had been previously involved in different kinds of shows of force, such as the denunciations for the sake of liberty that made up such a big part of conservation work. Now, by using the symbolic register of rebellion, they want their shows of force to communicate something else: namely their status as meriting regard, a status they imagined would take the form of a salaried or otherwise entitled relationship to the state. They hoped that the good intentions crowd’s involvement would help them leverage their demands for distribution. In this respect, the rebels have largely failed, or at least been disappointed. But while they have not achieved the kind of entitled status they hoped for, they have also enjoyed certain adventurous aspects of their careers and the new lifestyles and ideas they have encountered.

North-eastern Central African Republic, a vast space bordering Chad, Darfur, and South Sudan, is a quintessential ‘stateless’ space: the government has little presence and a variety of armed actors operate. This book investigates raiding, the distinctive political repertoire that people have developed to work here, tracking the evolution of raiding skills and encounters over the last 150 years, from the period of the trans-Saharan slave trade to colonial forced labour regimes, to big-game hunting and coercive conservation, and to rebellion. Raiding is a mode of forceful acquisition that flourishes when people’s status in relation to each other is unclear, and those pursuing it develop improvised skills including camouflage, displaying force, and denouncing, generally to make claims to extraction and liberty. Raiding has been particularly important in encounters between people who were unfamiliar with each other and potentially dangerous to each other, and who are working in a place where infrastructure and institutions offer little in the way of a guide to action. Instead, people must situationally manage the conflicts of values they inevitably experience, and ethical relations are marked by negotiation and confrontation, rather than a quest for consistency. While the book’s heart beats in Central Africa, raiding politics offer rich comparative insights that helps us better understand the vibrant, if not always salutary, place that forceful acquisition plays in the world today – in Central Africa and far beyond.

Chapter One explores ancestors of the idea that the physical sciences were relevant and significant to the study of obscure powers associated with the human body and mind. In the late eighteenth and early nineteenth centuries, practitioners of animal magnetism and mesmerism linked the study of a supposed new imponderable ‘magnetic’ fluid affecting health to better-known physical imponderables. In the mid-nineteenth century the German chemist Karl von Reichenbach and his followers stimulated much debate for their alleged discovery of new imponderable ‘od’ that they believed extended the domain of physics into the realm of physiology. From the 1840s onwards ’Modern Spiritualism’ prompted many natural philosophers to intervene on controversies over its startling physical effects. The final section of the chapter contextualises these attempts to link physical and psychical realms in terms of the fluid state of the physical sciences in the early and mid-nineteenth century.