Perhaps one of the most intriguing questions in philosophy concerns the true nature of external reality. In this paper, we discuss some of the theories that have been put forth regarding the nature of reality and of our perceived universe. We develop an abstract mathematical model, whereby, several theories that have been proposed so, ranging from modern physics to ancient Indian philosophy can be brought under a common umbrella. We also discuss a specific case, which emerges from our more general model, which has an interesting consequence upon the way we view our world.
Perhaps one of the most intriguing questions in philosophy concerns the true nature of external reality. In this paper, we discuss some of the theories that have been put forth regarding the nature of reality and of our perceived universe. We develop an abstract mathematical model, whereby, several theories that have been proposed so, ranging from modern physics to ancient Indian philosophy can be brought under a common umbrella. We also discuss a specific case, which emerges from our more general model, which has an interesting consequence upon the way we view our world.
I am very grateful to the Master and Fellows of Trinity College for inviting me to give the Tarner Lectures. What I want to do in this book, stated boldly and baldly, is to consider the relevance of developments in modern theoretical physics to metaphysical questions about the ultimate nature of reality. By metaphysical questions I mean the very general sorts of questions that arise out of a critical examination of the principles, concepts and fundamental presuppositions that lie behind modern physics. How should we interpret the claims that physicists seem to be making about the world? Are they intended to be understood as literally true, for example, and exactly what are those claims, given that the pages of theoretical physics monographs are largely filled with abstract mathematical formalism? In the first chapter, I shall be looking at a range of philosophical points of view in the framework of which such questions can be addressed, and attempt the difficult task of adjudicating between the different approaches. At the end of the day I shall be arguing for a pretty straightforward metaphysical realism, that the external world exists independently of our knowledge of it. In the second chapter I shall look at arguments from various branches of modern physics that are sometimes claimed to bring in an essential role for subjectivity in physics, bringing the observer into a central role, creating his own reality.
In this chapter, I offer some personal reflections about the nature of reality, shaped by my work as a quantum physicist, my experimentation with psychedelic drugs during the 1960s, and my more recent studies of modern cognitive science. Traditionally, questions about the essential nature of reality are asked by philosophers. In the twentieth century, these questions were asked for the first time by scientists as well. During the first three decades of the century, the exploration of the atomic and subatomic world brought physicists in contact with a strange and unexpected reality that shattered the foundations of their worldview and forced them to think in entirely new ways. Quantum physics showed scientists “a new reality,” and from that time on, the nature of reality became a popular subject of discussion not only in philosophy but also in science. In recent decades, cognitive scientists took another radical step in the scientific conception of the nature of reality. They asserted that the features of our ordinary, everyday reality are not features of an independently existing world, but are created in the very process of perception. In a way this generalizes the influence of the act of perception on the perceived object, which was famously analyzed in quantum physics by Werner Heisenberg, to everyday perception. In other words, even our everyday reality is just one of many alternate realities.
In classical physics there is, in accordance with common sense, an objective world ‘out there’. That world evolves in a clear and deterministic way, being governed by precisely formulated mathematical equations. This is as true for the theories of Maxwell and Einstein as it is for the original Newtonian scheme. Physical reality is taken to exist independently of ourselves; and exactly how the classical world ‘is’ is not affected by how we might choose to look at it. Moreover, our bodies and our brains are themselves to be part of that world. They, also, are viewed as evolving according to the same precise and deterministic classical equations. All our actions are to be fixed by these equations - no matter how we might feel that our conscious wills may be influencing how we behave. Such a picture appears to lie at the background of most serious 1 philosophical arguments concerned with the nature of reality, of our conscious perceptions, and of our apparent free will. Some people might have an uncomfortable feeling that there should also be a role for quantum theory - that fundamental but disturbing scheme of things which, in the first quarter of this century, arose out of observations of subtle discrepancies between the actual behaviour of the world and the descriptions of classical physics. To many, the term ‘quantum theory’ evokes merely some vague concept of an ‘uncertainty principle’, which, at the level of particles, atoms or molecules, forbids precision in our descriptions and yields merely probabilistic behaviour. Actually, quantum descriptions are very precise, as we shall see, although radically different from the familiar classical ones. Moreover, we shall find, despite a common view to the contrary, that probabilities do not arise at the minute quantum level of particles, atoms, or molecules - those evolve deterministically - but, seemingly, via some mysterious larger-scale action connected with the emergence of a classical world that we can consciously perceive. We must try to understand this, and how quantum theory forces us to change our view of physical reality.
It must have been around 1950. I was accompanying Einstein on a walk from The Institute for Advanced Study in Princeton to his home, when he suddenly stopped, turned to me, and asked me if I really believed that the moon exists only if I look at it. The nature of our discussion was not particularly metaphysical. Rather, we were discussing the quantum theory … (Abraham Pais, 1982) There is an old debate in philosophy about whether the world outside our minds exists at all. In the early-seventeenth century, Descartes pioneered the new mechanical and geometrical view of material reality in which every event was determined. But he also believed that we each had a soul and that our will was free. Thus he had to insist that matter and the soul were entirely different: the mind-body split was born. Descartes's critics soon pointed out that a soul confined within the “veil of perception” had no direct evidence that its perceptions were true. Perhaps they were mere illusions or some sort of cinematic film projected by God? Bishop Berkeley went so far as to suggest that there are no bodies outside the mind, and that perceptions were the only reality: “to be is to be perceived”. Samuel Johnson thought this was all twaddle. He famously rebutted Berkeley by kicking a stone, as if to say that its reality was painfully obvious. During the past 30 years, there has been a resurgence of these sorts of questions.
The concept of "reality" is often raised in the context of philosophical foundations of physics or interpretations of quantum mechanics. When this term is so raised, it is a warning to me that I am about to be led down a rabbit hole. Such diversions usually lead nowhere unless you consider endless discussions of Schrodinger's cat, wave function collapse, quantum non-locality, and parallel universes to be useful. A prime example is the famous Einstein, Podolsky, and Rosen paper wherein they concluded that the quantum wave function cannot provide a complete description of physical reality. In this essay I suggest that, in physics discourse, the term "reality" should be avoided at all costs.
The relationship between physical notions and the structures expressing them is an issue of primary importance the history and philosophy of pre-modern natural philosophy and of modern science. Historical evidence suggests that, when investigating the relationship between physics and mathematics, one should pay attention to the material, sensually perceivable forms mediating it: spoken or written words, drawings, artefacts, descriptions of experimental set-ups or, as the case discussed the present paper, symbolic notation. The reason for this is that, historically, physical notions and their expressions have very often been developed as one, and only distinguished from each other at a later stage. This was for example the case with what we today regard as mathematical and classical mechanics, which were developed the course of the eighteenth century as the discipline of the analysis of motion. When considered from a later point of view, both the physical notions and the concepts involved historical developments appear as being in flux, vague, and, as far as the side is concerned, non-rigorous. In such cases, verbal description, mechanical artefacts or symbols do not simply mediate between physical notions and structures, as might be the case at a later stage, but represent both of them one, allowing the historical actors to construct and manipulate physical-mathematical meaning by following, at times, their physical reasoning and, at times, their criteria of rigour. The history of quantum mechanics offers many examples of how new physics and new mathematics can emerge as one, with symbolic notation playing a central role shaping both. Among the many creators of quantum theory, Paul Dirac was particularly sensitive to questions of notation: