This chapter guides the reader through three related enigmas of modern physics. The first is a mystery of quantum mechanics. Important aspects of quantum mechanics are still not truly understood, although competing theories have been proposed, including the Many-Worlds approach. The second enigma is the emergence of spacetime, and especially the way it interacts with gravity. Rather than following the traditional methodology of ‘quantising’ classical theories, the author proposes an alternative approach and instead seeks gravity within quantum mechanics. The chapter concludes with a discussion of the mystery of the arrow of time: what distinguishes the past from the future. Together, these three mysteries of modern physics serve as an important reminder of the endurance of enigmas in the very foundations of scholarly fields. Re-examining founding principles can provide a constructive alternative means of investigating mysteries, not only in modern science but also across other disciplines.

This chapter considers three concepts that were central to popular articulations of quantum physics: wave–particle duality, the function of observation in Erwin Schrödinger’s wave-mechanics, and the idea that physics describes an insubstantial world, opposed to the world of common sense. Taking these concepts in turn, it shows that in Woolf’s novels, as well as in scientific radio broadcasts, in the popular science writing of G. P. Thomson, Arthur Eddington, and James Jeans, and in modernist culture more broadly, they become associated with the idea that identity is multiple. The first section, ‘Rays around a Point: Wave–Particle Duality’, examines a passage from The Wavesin relation to accounts of G. P. Thomson’s electron-diffraction experiment, which confirmed the wave–particle duality of matter. The second section, ‘“Its Beam Strikes Me”: Schrödinger’s Wave Equation’, considers the role of observation in limiting identity in The Waves and The Years, identifying resonances with popular accounts of Erwin Schrödinger’s wave function. Tthe last section, ‘“We Ripple in Light”: Insubstantial Selves’, examines the interplay between solidity and insubstantiality in Woolf’s novels and in contemporary popular science.

Under the international law of State responsibility, the existence of an internationally wrongful act requires that three cumulative conditions be fulfilled: (1) attribution of a conduct to the State; (2) breach of a State’s international obligation by that conduct; and (3) a lack of circumstances precluding the wrongfulness of that conduct. A finding that such an internationally wrongful act occurred entails certain legal consequences, which in particular requires the State to provide full reparation for the damages caused. Chapter 15 analyses how these rules apply in the context of investor–State arbitration. More precisely, it focuses on attribution, circumstances precluding wrongfulness and reparation, with Part II of the textbook setting out a discussion of the relevant breaches of IIA obligations. This analysis is conducted in light of the relevant treaty and arbitration practices as well as the Articles on Responsibility of States for Internationally Wrongful Acts, which are almost systematically referred to by arbitration tribunals when dealing with those matters.

This chapter is an overview, placing the body of work described in this book in perspective and describing its overarching structure, namely, how the three levels of structure are related: quantum field theory in curved spacetime established in the 1970s, semiclassical gravity developed in the 80s and stochastic gravity introduced in the 90s, a manifestation of the almost ubiquitous existence of a semiclassical and a stochastic regime in relation to quantum and classical in the description of physical systems. We describe the main physical issues in semiclassical and stochastic gravity, namely, backreaction and fluctuations, the mathematical tools used, and their applications to physical problems in early universe cosmology and black hole physics. In terms of connection to related disciplines, it is pointed out that the popular Newton–Schrödinger equation cherished in alternative quantum theories does not belong to semiclassical gravity, as it is not derivable from quantum field theory and general relativity. However, stochastic gravity is needed for quantum information issues involving gravity. These theories enter even in the low-energy, weak-gravity realm where laboratory experiments are carried out. We finish with a summary of the contents of each chapter and a guide to readers.