In 2010, the media gave a lot of coverage to a book on popular science by Stephen Hawking and L.Mlodinow, The Grand Design. I think it is time to make a few comments, which I am going to introduce by means of quotations of the book:
· Philosophy is dead… Scientists have become the bearers of the torch of discovery in our quest for knowledge.
These words appear at the beginning of the first chapter. Although most of the book is just popular science, or history of science, it is ironical that the only original contribution (model-dependent realism) is purely philosophical.
· Objective reality is unknowable, therefore we cannot assume it exists... Only the results of observations and the model we build to explain them exist... Every model is valid (real) in its own field of application... Two models with the same explaining power are equally valid... Ptolemy's model is as valid as Copernicus's... Their only difference is the fact that the second is simpler than the first.
The preceding text is not a literal quotation, but a summarized paraphrase of chapter 3, which describes model-dependent realism, the original contribution of the book (with Berkeley's permission). The authors forget that Copernicanism predicted correctly the stellar parallax, which cannot be explained in Ptolemy's. In the same chapter, Hawking and Mlodinow discard the steady state cosmological theory because it is unable to explain certain observations on the universe. Shouldn't they do the same with Ptolemy's?
· [The universe] doesn't have a single history, but every possible histories… The past is indefinite and exists only as a spectrum of possibilities.
These assertions in chapter 4 come in the context of a discussion on Richard Feynman's formulation of quantum mechanics, a mathematical device alternative and equivalent to Heisenberg's matrix mechanics or Schrödinger's wave function, which computes the probability of a quantum event by integrating over all its possible trajectories. To derive those conclusions, Hawking y Mlodinow need that the indicated mathematical device should represent reality in some way (the same reality whose existence they deny). This is the reason why they have invented model-dependent realism. But they don't even mention the paradoxes which happen when these theories are applied to macroscopic objects, such as Schrödinger's cat, while they apply them happily to the whole universe, without any justification. Also, hadn't they said that reality is unknowable? Then how can we know that the universe exists? The authors do not bring up this problem, perhaps because it would lead them into a contradiction.
· How can one tell if a being has free will?... We cannot even solve exactly the equations for three or more particles interacting with each other. A [being] the size of a human would contain about a thousand trillion trillion particles… it would be impossible to solve the equations and predict what it would do.
This discussion in chapter 8 is absurd. A mechanical calculator also has a trillion trillion particles. However, observing its past and present behavior, we can deduce easily that it does not have free will and predict its future behavior. The authors forget that the behavior of macroscopic beings can be analyzed without the need to apply particle physics. And the idea of free will does not come from solving equations, but from introspection.
· There is no restriction on the creation of whole universes… Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist.
Assuming that this is true (a huge assumption), we still should explain why there are laws that allow this to happen, so we are still in the same position. On the other hand, everything the book says about the multiverse as a possible explanation of fine tuning adds nothing new to what we already know.
Scientists who try to work philosophy (the same philosophy that they spurn and consider dead) should take the trouble to study it in a little more depth. At least, they would be more careful not to violate some of its fundamental supports, such as the principle of no contradiction. This criticism applies, not only to Hawking, but also to other well-known scientists, such as Richard Dawkins, who dare to invade the field of philosophy and display their ignorance.
It's a pity that the philosophical errors it contains may discredit the whole book I am commenting. Although it comes from mere philosophical amateurs, it would be nice if the only original proposal of The Grand Design (model-dependent realism) were studied more in depth by professionals.
I'll end with a quotation by Woody Allen (Getting even, 1971):
Is knowledge knowable? If not, how do we know this?