Weinberg returns to the “The Cosmological Constant Problem” and suggests an anthropic principle solution. Anthropic reasoning could make it possible for us to calculate the effective vacuum energy. Observations of dark energy in 1998 show that the expansion of the universe is accelerating. This observational result is not inconsistent with the notion of a possible multiverse – the issue has not been settled.

The possibility of the multiverse bean with early steady-state theories postulating causally unconnected regions, a standard Big Bang where spatial cross-sections are flat or open, or even an eternal inflationary universe. These cosmological options present a philosophical challenge to a realist understanding of the universe that is addressed through a discussion of the CMB’s central relevance in it in the chapter.

This chapter addresses the graphic novel as a new form of the “Great American Novel” (GAN). This possibility is seen as the result of two interacting processes: canon formation (Which are the graphic novels that can gain inclusion into the mainstream canon?), and literary validation (Can graphic novels be judged with the same criteria as literary novels?). The chapter discusses the critical debates on the recognition of comics as a form of literature and the role of academia and other institutions in the making of a graphic novel canon. It studies the progressive literarification of comics and graphic novels, before focusing on the notion of the GAN, a label that refers to works picturing the ordinary emotions and manners of American existence (J. W. DeForrest), preferably with a high degree of realism. The chapter critically discusses this notion and concludes with a close reading of four graphic novels that constitute good candidates for the title of GAN: Ghost World, Fun Home, American Born Chinese, and Asterios Polyp.

Editors and critics have struggled to place The Merry Wives of Windsor within the framework of Shakespeare’s chronicle history plays, and it is often said that the Falstaff of Merry Wives is a different character from that of the histories. Merry Wives can be seen as part of a multiverse, of incompatible timelines in which characters are both entirely familiar and somehow altered. In the multiverse of Merry Wives, both public and private histories are apparently erased. While the history plays are burdened by almost pathological remembrance and rumination, the world of Merry Wives shows the advantages of amnesia.

Here we discuss inflation, a period of accelerated expansion that occurred in the very early history of the universe. We motivate inflation by describing the flatness and horizon problems, then explain how inflation resolves them. We describe the early history of inflationary ideas, then move on to modern work where we outline the standard scalar-field model for inflation, and define the slow-roll parameters that phenomenologically describe the dynamics of inflation. We briefly outline how inflation leads to the generation of density fluctuations in the universe; we mathematically describe the spectrum of these fluctuations, and confront it with modern observations. We end by discussing more speculative ideas in this area, including eternal inflation and multiverse.

This chapter has two combined aims. First, I point out that the standard fine-tuning argument for the multiverse, as discussed in the previous two chapters, differs crucially from paradigmatic instances of anthropic reasoning such as, notably, Dicke's and Carter's accounts of large number coincidences between large numbers in cosmology. The key difference is that the standard fine-tuning argument for the multiverse treats the existence of forms of life as calling for a response and suggests to infer the existence of a multiverse as the best such response. Anthropic reasoning of the type championed by Dicke and Carter, in contrast, assumes the existence of forms of life as background knowledge when assessing whether the large number coincidences are to be expected, given the competing theories. The second aim of this chapter is to propose a new fine-tuning argument for the multiverse, which – unlike the standard one – is structurally similar to Dicke's and Carter's accounts of large number coincidences. The new argument turns out to have the virtue of being immune to the inverse gambler's fallacy charge.

The most-discussed objection against this argument is that it commits the inverse gambler's fallacy, originally identified by Ian Hacking. This fallacy consists in inferring from an event with a remarkable outcome that there have likely been many more events of the same type in the past, most with less remarkable outcomes. I discuss several suggested analogs to the problem of the fine-tuned parameters. Ultimately, as I argue, established standards of rationality may just not allow one to decide whether the standard fine-tuning argument for the multiverse commits the inverse gambler’s fallacy or not. Some of the considerations in this chapter, as explained along the way, are relevant to the debate about the Fermi paradox.

Multiverse theories are physical theories according to which we have empirical access only to a tiny part of reality that may not be representative of the whole. The idea that we might live in a multiverse is often suggested as a response to the finding that various parameters seem fine-tuned for life. The combination of string theory and inflationary cosmology is taken to propose a specific implementation of the multiverse idea: the landscape multiverse. I review these lines of thought and outline the structure of the book. I also highlight its central theses and ideas.

This chapter continues the discussion of the standard fine-tuning argument for the multiverse, switching to the language of Bayesianism. After highlighting the desideratum of motivating a non-negligible (ur-) prior for the multiverse, I assess a worry, due to Cory Juhl, about belief in the multiverse, as based on the standard fine-tuning argument for the multiverse: that, even if the inverse gambler's fallacy charge could be rebutted, such belief would inevitably rely on illegitimate double-counting of the fine-tuning evidence. I argue that this concern can be assuaged, at least in principle: it is coherently possible for there be empirical evidence in favor of some specific multiverse theory – and thereby, derivatively, for the generalized multiverse hypothesis – whose evidential impact is independent of the fine-tuning considerations. The probabilistic formalism is also used to clarify why it is so difficult to determine whether the standard fine-tuning argument for the multiverse is fallacious: the difficulty can be linked to an ambiguity in the background knowledge based on which the impact of the finding that the conditions are right for life in our universe is assessed.

This article grew out of my February 2017 Scientific American column titled “Imagine No Universe,” eventually expanding into a feature-length cover story for Skeptic, necessarily an order of magnitude longer to nuance the many possible answers to the question. As readers will discover, far from a famine of scientific and philosophic answers to the question, we have a veritable feast to dine on. Which will turn out to be more or less supported by empirical research in both particle physics and cosmology remains to be seen – and it could be many decades to a century before we have a solid grasp of the problem – but do not succumb to the theists’ transcendental temptation to evoke God as an answer in the teeth of so many elegant explanations already on our plate.