God and Stephen Hawking by John Lennox Read Free Book Online Page A

speculative, but testable and well within the zone of evidence-based rational thought.
    Modelling reality: the nature of perception
     
    Since Hawking understands M-theory to be a model, it is important to say a few words about Chapter 3 of his book, where he explains his view of mathematical theories as models. Using an analogy of a goldfish that sees the world through the distorting lens of its bowl, Hawking affirms:
    There is no picture- or theory-independent concept of reality. Instead we will adopt a view that we will call model-dependent realism: the idea that a physical theory or world picture is a model (generally of a mathematical nature) and a set of rules that connect the elements of the model to observations … According to model-dependent realism, it is pointless to ask whether a model is real, only whether it agrees with observations. 58
     
    Roger Penrose is less convinced by this anti-realism. Referring to Hawking’s stance, he writes: “My own position, on the other hand, is that the issue of ontology is crucial to quantum mechanics, though it raises some matters that are far from being resolved at the present time.” 59 In his review of The Grand Design he records his antipathy to subjectivity:
    Among Einstein’s difficulties with current quantum mechanics was its leading to subjective pictures of physical reality – as abhorrent to him as to me. The viewpoint of “theory-dependent realism” being espoused in this book appears to be a kind of half-way house, objective reality being not fully abandoned, but taking different forms depending upon the particular theoretical perspective it is viewed from, enabling the possibility of equivalence between black and white holes.
     
    Penrose then comments on the “goldfish bowl”:
    An illustrative example the authors provide involves goldfish trying to formulate a theory of the physical space outside their spherical goldfish bowl. The external room appears to them to have curved walls, despite being regarded as rectilinear by its human inhabitants. Yet the goldfish’s and human’s viewpoints are equally consistent, providing identical predictions for those physical actions accessible to both life forms at once. Neither viewpoint is more real than the other, being equivalent for making predictions.
I do not see what is new or “theory-dependent” about this perspective on reality. Einstein’s general theory of relativity already deals with such situations in a completely satisfactory way, in which different observers may choose to use different co-ordinate systems for local descriptions of the geometry of the single fixed over-reaching objective space-time. There is a degree of subtlety and sophistication in the mathematics, going significantly beyond what is present in Euclid’s ancient geometry of space. But the mathematical “space-time”, whereby the theory describes the world, has complete objectivity [italics mine].
It is nevertheless true that current quantum theory presents threats to this objectivity of classical physics (including general relativity) and has not yet provided an accepted universally objective picture of reality. In my opinion, this reflects an incompleteness in current quantum theory, as was also Einstein’s view. It is likely that any “completion” of quantum theory to an objective picture of reality would require new mathematical ideas of subtlety and sophistication beyond even that of Einstein’s general-relativistic space-time, but this challenge is addressed to future theorists’ ingenuity and does not, in my view, represent any real threat to the existence of an objective universe [italics mine]. The same might apply to M-theory, but unlike quantum mechanics, M-theory enjoys no observational support whatever. 60
     
    Hawking’s view of reality is derived from what he thinks about human perception. He says that perception is “not direct, but rather is shaped by a kind of lens, the interpretive structure of our