Perceptual Modal Collapse is the view that no unperceived perceptibles exist. Aristotle takes Perceptual Modal Collapse to be central to Protagoreanism. But Aristotle’s Categories 7 commits Aristotle to Perceptual Modal Collapse: perception and perceptible correlate; each relative pair is constituted by its relation to its correlative; correlatives exist at all the same times; so, perception and perceptible exist at all the same times. Hence, there are no unperceived perceptibles. Moreover, correlatives are simultaneous by nature. Aristotle’s arguments that this does not apply to perception and perceptible are unconvincing. I argue that Aristotle’s second definition of relatives can save Aristotle’s theory from Perceptual Modal Collapse, since the definition distinguishes perceptible as a schematic relative from specific perceptible qualities. Once we disambiguate, we can see that specific perceptibles need not exist at the same time as perceptions. Thus, the specific heat of a fire in a forest can exist, even when unperceived. These ideas underlie Aristotle’s account of intentional relatives in Metaphysics 5.15, where specific perceptual qualities are the content of perceptions.

Protagoras, the sophist of the fifth century BCE, has long been associated with relativism. This chapter examines what claims Protagoras may have made and whether these claims amount to some kind of relativistic worldview or not. It examines historical evidence, namely his famous “Measure Thesis” (DK 80 B1=LM PROT. D9), which is often supposed to be the first declaration of relativism, and Plato’s critical examination of it in the Theaetetus. Although it is important to consider the difference between relativism and relationalism or relativity, the example used in the Theaetetus, that “the wind is cold for me / is not cold for you”, can be understood in either way, so we find that Protagoras’ thesis was too vague and ambiguous to determine its original meaning. The ambiguities in the thesis are probably due to the author’s intention, and this blurring between relational and relativistic may also be part of his original plan. If so, Protagoras has contributed to philosophy by undermining the traditional view of truth and raising important and stimulating questions about relativism in the history of philosophy.

Relativity plays an important role in the skeptical outlooks of the Pyrrhonian skeptic Sextus Empiricus and of his predecessor Aenesidemus. But in the evidence concerning the earliest phase of Pyrrhonism, that of Pyrrho himself and his disciple Timon, there is no explicit mention of relativity. Nevertheless, there is good reason to suppose that it played an important role in their thinking. This is suggested both by the remarks at the opening of Diogenes Laertius’ life of Pyrrho, and by the summary by the Peripatetic Aristocles of an account by Timon of the early Pyrrhonist outlook. There is much about both these texts that is in dispute: whether they express a metaphysical view or epistemological reservations, whether the view applies only to questions of value or is global in character, and, on the Aristocles passage, how much of it represents Pyrrho’s ideas and how much just Timon’s. But on any plausible reading of these passages, there is a clearly implied emphasis on the variable ways in which things strike us, and this suggests a fundamental interest in relativity, even if it never surfaces explicitly.

One of the many fascinating ideas explored in Plato’s Sophist is the Stranger’s explanation of being relative-to through his account of the kinds being and difference in conjunction with the notions of capacity and combination, as well as what he invokes as the “forms” “itself by virtue of itself” and “relative to.” The discussion is remarkable in its clever use of an array of characters including Parmenides, the Pluralists, the Earthborn materialists, the Friends of the Forms, and the Late-learners to sort through a variety of challenging philosophical concerns, retaining what works while leaving behind what does not. The Stranger understands being as an intrinsic functional and structural dimension of all beings that makes them beings. Being just is capacity and the concurrent active “realizing” of capacity in “combinings” of forms with themselves and perceptibles. In lieu of an ontology of relations, there is an ontology of realizations of capacity relative to something. I show how this innovative account of a dynamic constellation of interwoven kinds and forms, where being and difference “go through all and each other,” provides a foundation for meaning, truth, and falsehood.

This appendix derives the momentum carried by electromagnetic fields and rewrites the Lorentz force law as a conservation law for total momentum in matter plus fields. Starting from the volume integral of ρE + J × B, it uses Maxwell’s equations to express the mechanical momentum change in terms of the fields alone, identifying a field momentum density ε0 E × B and introducing the Maxwell stress tensor as the flux of electromagnetic momentum through a surface. The resulting continuity equation states that changes in mechanical plus field momentum inside a volume are balanced by stress-tensor fluxes across its boundary. The appendix interprets this structure in terms of forces exerted on material bodies and the momentum carried by light, connecting the momentum density to the Poynting vector via g = S/c2.

This chapter reopens the archive of so-called romantic Arabic poetry to ask “how romantic,” both as a question of definition (how was it romantic, exactly?) and as a question of degree (how romantic was it, really?). Drumsta offers a few microscopic glimpses at the archive of interwar Egyptian poetry and criticism that illustrate how dramatically aesthetic theories, poetic terminology, and critical “frames of reference” – to borrow a term from Einstein’s special theory of relativity – were shifting in this period, and not necessarily or always in the direction of the romantic. First, Drumsta analyzes the second of two essays by the poet and critic ʿAbbās Maḥmūd al-ʿAqqād (1889–1964) titled “Shawqī in the Balance” (Shawqī fī al-Mīzān) from the 1920–1921 periodical al-Dīwān. Although al-ʿAqqād does not specifically invoke Einstein or relativity in al-Dīwān, his willingness to strike so decisively at the basic foundations of Arabic poetry and aesthetics mirrors Einstein’s approach to his period’s widely accepted principles of physics, and in this, the chapter suggests, al-ʿAqqād is a decidedly modern thinker.

Some modern implementations of vector concepts rely heavily on a precise knowledge of time. Measurements of time, both ancient and modern, have always been heavily tied to Earth’s rotation, and so this rotation must be described in detail. I begin that task by describing Earth’s orientation relative to the solar system and the stars, and use a DCM to quantify Earth’s orientation at a given moment. This introduces the idea of Universal Time, UT1. Further concepts require a short discussion of relativity, both special and general, which I do by using a balloon to describe curved spacetime. The result is UTC, our modern ‘Greenwich Mean Time’. Measuring time over long periods is made easy through the concept of the Julian day, and so I discuss the Julian and Gregorian calendars. I include a detailed example of using these ideas to calculate the sight direction of a star at some time and place on Earth.

Matthew Duncombe’s chapter ‘Relative Concepts’ asks: what are relative concepts according to ancient philosophers? Duncombe argues that Plato, Aristotle, and the Stoics have a clear concept of relatives, distinct from incompleteness approaches, which he calls ‘constitutive relativity’. The core idea of constitutive relativity is that a relative is constituted precisely by the relation it bears to an exclusive correlative. Duncombe discusses particular philosophers and schools in detail. The examination of Agathon’s speech in Plato’s Symposium illustrates that Socrates understands relative concepts in general and love in particular, on the constitutive model. Aristotle’s concept of relatives in Categories 7 draws on Plato, but Aristotle addresses a worry that relative concepts might be vacuous. Duncombe argues that a Stoic relative concept is the concept of a relative that relates exclusively to a correlative. He examines Sextus’ sceptical argument, which raises a worry about any conception of relativity where relatives relate exclusively to their correlatives.

The end result of Einstein’s revolutionary vision is that gravity is simply the manifestation of the curvature of spacetime. This is a concept that has a deep significance and is at the heart of the Einstein field equations. This Chapter will explain why we need to introduce the idea of 'spacetime' and how we can define the concept of spacetime curvature in this description. Starting from the example of a spacetime empty of matter – that is, a flat spacetime – we will move to the example of a spacetime containing matter and energy – that is, a curved spacetime. This chapter will explain why we find the description of gravity proposed by Newton very reasonable and why we have trouble appreciating the new vision proposed by Einstein. We will contrast the two descriptions with a simple example and show how the very same physical phenomenon – the orbit of the Earth around the Sun – can be seen with very different explanations by Newton and Einstein.

The term ‘social exclusion’ appears to have originated in France in the 1970s and had a significant influence on European social policy before being taken up by the UK’s New Labour Government in the 1990s. This chapter outlines the concepts of social exclusion and some of the competing discourses associated with the term. Several notable definitions of the term are discussed before we settle on the CASE definition of ‘An individual is socially excluded if he or she does not participate in key activities of the society in which he or she lives’. The concepts of social exclusion may provide added value to discussing the more traditional concepts of poverty and deprivation. It is a relational concept and thus is of importance for developing a social psychiatric perspective. The relationship between Social Exclusion and Social Inclusion is complex and they are not necessarily polar opposites; rather, they may be viewed as a continuum, but a continuum of several dimensions which may differ over time and place. The chapter sets out a framework for examining the social exclusion of people with mental health conditions.

A brief history of the discoveries and their subsequent development gives an introduction to the research topics dealt with in later chapters: pulsar searches, precision timing, positions and identifications, millisecond pulsars, binary systems, neutron star structure, general relativity, emission mechanisms, fast radio bursts, interstellar medium.

The interest taken by Surrealists in alchemy has been well known since the late 1940s, but knowledge of their preoccupation with modern science is more recent. This chapter observes the Surrealist penchant for premodern, occultist epistemologies before focusing on their take up of modern physics in the early 1920s. The theory of relativity (1905 and 1915–16) and developments in quantum mechanics (1922–7) were then undergoing popularization. Apart from popular articles in newspapers/journals, this occurred partly through physicists’ own writings and partly through the philosophy of science. This chapter indicates the importance to Surrealism of the writings of the French philosopher of science, Gaston Bachelard. It also features a case study of the work of German physicist Pascual Jordan whose attempt to extend the findings of quantum mechanics to biology was known to Max Ernst and used by the Surrealists to justify the rejection of positivism. So modern physics became a means of retrospectively comprehending the Surrealists’ turn towards automatism and Ernst’s own natural history incursions. His response to Jordan’s writings offers an alternative way of reading his work.

This chapter examines the changing relations between Mach’s epistemology and his mechanics to offer a new perspective on the diverse respects in which Einstein built on Mach’s work. Considering Mach’s early psychophysical research on sensations of space and time indicates foundations both for Mach’s later research on physical space and time and for his search for an epistemology capable of encompassing conceptions and perceptual experience, but also psychology, physics, and psychophysics, as well as the social world: all knowledge. I show that Mach’s critical studies of mass and inertia emerged from his perceptual studies and were intimately linked to bodily experience and experiment. Considering his well-known Mechanics indicates that Mach sought to train the imagination as well as stimulate critique in the attacks on absolutes that are now usually taken to define his anti-metaphysical empiricism. I argue that while celebrating the role of Mach’s criticism, Einstein remained unaware of the extent to which his initial approach to general relativity was shaped by a pedagogical thought experiment on action and reaction in which Mach linked gravitation and acceleration. Finally, when he turned explicitly to epistemology, rather than emphasising positivist empiricism, Mach offered a study of the psychology of research in practice.

“Anaximander for the Anthropocene” presents a formal sketch of modern complexity theory, then argues that the cosmological propositions of Anaximander of Miletus represent a style of rational thinking in Greek antiquity, founded on analogy, to which modern systems science owes an unacknowledged debt. The systems approach to the world first adumbrated by Anaximander’s natural philosophy, it is suggested further, provides the conceptual basis for any meaningful sustainability ethos, even in the modern age.