The argument and recent physics and cosmology

The historical context of the argument helps clarify its intentions. Consider four such contexts: the physics and cosmology of the last few decades, the physics of the first half of the twentieth century, the rise of the life sciences and their relation to physics, and the study of human history and society. To place the argument in these multiple contexts is to understand how much is at stake in these disputes. It is also to undermine the fake authority that clings to widespread ideas about the plurality of worlds, the restricted reality of time, and the power of mathematics to serve as a privileged window on reality.

In its relentless quest for a definitive unification – a view that would bring gravity under the same theories that account for the electromagnetic, the strong, and the weak forces – much of contemporary physics and cosmology has despaired of explanations that meet the traditional and exacting standards of either deterministic or probabilistic causality. It has settled for explanations that admit a vast array of states of affairs, of which the observed states of affairs represent no more than particular variations. Rather than acknowledging such underdetermination as a limit or a failure of insight, it has tried to turn a detriment into a benefit by describing the former as the latter.

The conception of the singular existence of the universe introduced

There is one real universe. This universe may extend indefinitely back in time, in a succession of earlier universes or of earlier states of the universe. We have no sufficient reason to believe in the simultaneous existence of other universes with which we have, and cannot have, now or forever, causal contact.

Causal communion is the decisive criterion for the joint membership of natural phenomena in the same universe. The parts of a universe are causally connected, directly or indirectly, to all the other parts over time. Over time is the first and most important qualification. Two parts of nature belong to the same universe if they share any event in their causal past, even if they have subsequently become causally disjoint. It is the network of causal relations viewed backward into the past that determines the scope of causal communion and thus the separate existence of a universe. The criterion is dynamic rather than static, historical rather than exclusively structural, and presupposes the reality of time.

In Chapter 1, we surveyed the experimental and observational situation in cosmology and proposed five principles which we believe must constrain the construction of any properly cosmological theory:

1. The principle of differential sufficient reason.

2. The principle of the identity of the indiscernible.

3. Explanatory closure.

4. No unreciprocated action.

5. Falsifiability and strong confirmability.

Having set the scene, we now propose three hypotheses which we suggest should guide the discovery of a cosmological theory which satisfies these principles. I will state the hypotheses and then discuss each in turn.

1. The uniqueness of the universe.

2. The reality of time.

3. Mathematics as the study of systems of evoked relationships, inspired by observations of nature.

Someone might call these also principles, but I want to stress that the first two are hypotheses about nature, which might be confirmed or disconfirmed as science progresses. They have force because they suggest different kinds of experiments and different results than approaches which deny them or embrace hypotheses which conflict with them.

Now I elaborate on each of these.

We close as we opened, with the crisis in cosmology. The growth of untestable scenarios about unobservable multiple universes or extra dimensions are not a cause of the crisis, they are a symptom of the need to change paradigms to avoid stumbling over unanswerable questions, or the proliferation of untestable hypotheses. The great universities and research institutes are full of theoretical physicists who would like to be Albert Einstein, but have no idea how to do it. If so many people of undeniable talent and dedication are unable to make progress, the reason must be in a common mistake, a common shared assumption that is incorrect.

In this book we have aimed to identify the wrong assumptions and conceptual mistakes that are leading cosmology away from the disciplines of science into untestable speculations. They begin with the cosmological fallacy: the mistake of taking a scientific methodology, the Newtonian paradigm, outside of the domain where it can make contact with experiment and observations. The first step in our argument is the understanding that the Newtonian paradigm can only be used in the description of small subsystems of the universe.

The main test of the ideas we have argued for, as of any new scientific ideas, is whether they generate a new agenda for research in science that succeeds in generating new knowledge even as it instigates a new paradigm for the organization of our ideas about nature. In this last chapter of this book I show that it is already doing so. The main fields affected are cosmology, quantum gravity, and the foundations of quantum theory.

The agenda for observational cosmology

The first field affected by our program is cosmology, where indeed there already is a split between those investigating pluralistic models of cosmology and those developing models based on a succession of universes. We have said enough about the failure of many-universe cosmologies to generate falsifiable predictions (but for those readers needing more convincing of this, see [7, 10, 9]) and need only contrast this with the genuine predictions generated by cosmological scenarios which assume the big bang is not the first moment of time, but a passage before which the universe existed, if possibly under different laws. Three examples, discussed above, suffice to demonstrate the claim that such successional hypotheses can and do generate falsifiable predictions for doable experiments.

• The cyclic cosmologies of Steinhardt, Turok, and collaborators make two predictions for the structure of the fluctuations in the CMB which strongly distinguish them from predictions of generic inflation models [56]. (The qualifier “generic” is necessary because inflation models can be fine-tuned to generate diverse predictions.) These are an absence of tensor modes and a significant non-Gaussianity. Both predictions are being tested in data from the Planck satellite which is being analyzed as of this writing.

In Chapter 1, I introduced the metaphysical folly as the tendency for unreflective naturalists to believe in an imagined nature constructed in their imaginations as being more real than the world we perceive with our senses.

A symptom of the metaphysical folly is the move from Sense impressions give unreliable knowledge of nature, nature is instead truly X to Sense impressions are incompatible with the concept that the world is X, so qualia must not exist. But the one thing we can be sure of is that qualia exist. Therefore, as Galen Strawson [85] and other philosophers of mind [86] emphasize, if we are naturalists and believe everything that exists is part of the natural world then qualia must be also part of the natural world. The right statement – if we are naturalists – must be:

Here I would like to argue that it is much easier to conceive of qualia as part of the natural world in temporal naturalism than in timeless naturalism.

The principles and hypotheses we present in this book become a research program when we see that they can be implemented in particular theories and models. As we have argued, such a theory must be based on the idea that the laws of nature evolve in a real, global, cosmological time. These must avoid the cosmological dilemma and fallacy and so cannot be expressed within the Newtonian paradigm, yet they have the task of providing sufficient reason for the laws and initial conditions that govern subsystems of the universe. We can call the problem of framing this new paradigm of explanation the meta-law problem, because the issue is to discover how and why laws evolve. This must be done in a way that avoids the meta-law dilemma.

It is natural to describe the evolution of laws by means of an imagined space of possible laws. The evolution of laws can then be visualized and studied as evolution of either an individual universe or a population of universes on this space of possible laws. In the first case, for example, we have a sequence of points representing the laws that hold in different eras of a universe. The space of possible laws has come to be called the landscape; this terminology was first introduced in the context of cosmological natural selection and was chosen to evoke thoughts of the fitness landscapes that are studied in models of population biology [8]. In some, but not all, work on the landscape, it is assumed that the possible laws represented by points of the landscape are perturbative string theories, each an expansion around a vacuum state of string theory, which is in turn a solution to a meta-theory such as M theory. In these cases we refer to the landscape of string theory.

The problem

A view of mathematics and of its relation to nature and to science complements the two ideas that are central to this argument: the idea that there is one real universe (as opposed to a multiplicity of universes, of which our universe would represent one) and the idea that time is real and touches everything (with the consequence that everything, including the laws of nature, changes sooner or later). These ideas make trouble for received accounts of mathematics and of its applicability in the scientific study of nature: they cannot be adequately accommodated within any familiar interpretation of the nature of mathematics. They require a different approach.

The core of this conception is that mathematics is an understanding of nature emptying the world out of all particularity and temporality: that is, a view of a world without either individual phenomena or time. It empties the world out of them the better to focus on one aspect of reality: the recurrence of certain ways in which pieces of nature relate to other pieces. Its subject matter are the structured wholes and bundles of relations that outside mathematics we see embodied only in the time-bound particulars of the manifest world.

To think of the universe as a whole rather than of something within the universe is one of the two most ambitious tasks that thought can undertake. Nothing matches it in ambition other than our attempts to form a view of ourselves. In addressing this topic, we soon reach the limits of what we know and even of what we can ever hope to know. We press science to the point at which it passes into philosophy and philosophy to the point at which it easily deceives itself into claiming powers that it lacks.

Yet we cannot cast this topic aside. First, we cannot avoid it because we are driven to understand whatever we can about our place in the world, even if what we do know, or might discover, represents only a small and superficial part of the enigmas of nature. Second, we should not seek to escape it because no one can develop and defend ideas about parts of natural reality without making assumptions, even if they remain inexplicit, about nature as a whole. Third, we need not turn away from it because among the greatest and most startling discoveries of science in recent times are discoveries about the universe and its history. The most important such discovery is that the universe has a history. Part of the task is to distinguish what science has actually found out about the world from the metaphysical commitments for which the findings of science are often mistaken.

Changing laws

Do the laws of nature change? Many philosophers and scientists have claimed that the immutability of the laws of nature is a premise of the work of science. In pressing this claim, they reify a particular idea of science: an idea that takes the central tradition of physics, from Newton to Einstein, as the model of science. For it is only in this tradition that the notion of changeless laws of nature has had a secure place. Nevertheless, only very few physicists, Dirac and Feynman first among them, have explicitly questioned the immutability of the laws of nature and suggested that they must have been different in the early universe.

There are other branches of science in which the notion of unchanging laws does not immediately occur to a practicing scientist unless he is anxious to show how his scientific practice can be made to conform – or to appear to conform – to the supposed master science, modern physics. We commonly think of the explanatory force of the regularities of natural evolution that are enshrined in the contemporary Darwinian synthesis as having developed together with life. This joint transformation of the phenomena and of the regularities that they exhibit is not a one-time phenomenon; it keeps happening. For example, our account of the workings of the Mendelian mechanisms in the course of evolution is modified by the arrival of sexual reproduction.