In his recent best seller, the world's most famous scientist proclaims that philosophy is dead. But those who ignore philosophy are condemned to repeat it. And those who disparage philosophy are usually slaves of some defunct philosopher.
In The Grand Design, Stephen Hawking and fellow physicist Leonard Mlodinow declare on the first page that philosophy is dead, because it has not kept up with modern developments in science. They then proceed to make a series of philosophical pronouncements, including the following:
A. "There is no picture- or theory-independent concept of reality."
B. "A model is a good model if it:
1. Is elegant
2. Contains few arbitrary or adjustable elements
3. Agrees with and explains all existing observations
4. Makes detailed predictions about future observations that can disprove or falsify the mode if they are not borne out."
C. "A well-constructed model creates a reality of its own."
Of these, A is true only if you accept (as I do) the view that concepts depend on theories. B is fairly consistent with the way in which philosophers of science talk about science, although it is perhaps a conceit of mathematical physicists to place elegance ahead of experimental support. But C is highly contentious in proposing that models can create rather than approximately discover reality. Obviously these assertions are all philosophical in making general claims about the nature of knowledge and reality.
Hawking and Mlodinow assume a connection between their philosophical claims and what they take to be scientific conclusions such as:
D. "The universe does not have just a single existence or history, but rather every possible version of the universe exists simultaneously."
E. "The universe itself has no single history, nor even an independent existence."
F. "We now have a candidate for the ultimate theory of everything, if indeed one exists, called M-theory."
G. "M-theory predicts that a great many universes were created out of nothing"
H. "The universe, according to quantum physics, has no single past, or history."
I. "The universe doesn't have just a single history, but every possible history, each with its own probability."
Hawking and Mlodinow state these general claims as if they were consequences of quantum mechanics, which has had a huge amount of empirical support. But the claims are not consequences of quantum theory as such, only of particular philosophical interpretations, of which there are more than a dozen, all highly controversial. Physicists agree that quantum theory provides successful predictions, but there is much disagreement about how to understand that success. Many eminent physicists, from Einstein to Lee Smolin, have questioned the kind of interpretation of quantum theory assumed by Hawking and Mlodinow, whose discussion of multiple universes is through-and-through philosophical, not straightforwardly scientific in the way they pretend. Like string theory on which it is based, it is difficult to find direct experimental support for M-theory. Hence Hawking and Mlodinow are deriving philosophical conclusions from a shaky interpretation of a controversial scientific theory.
What is the proper relation between philosophy and science? Once answer is the naturalist view, exemplified by philosophers such as Aristotle, Locke, Hume, Mill, Peirce, Dewey, Quine, and many contemporary philosophers of science. On this view, philosophy and science are continuous, so that fundamental questions about the nature of knowledge, reality, morality, and meaning should be addressed by taking into account scientific theories and evidence. In my recent book, The Brain and the Meaning of Life, I defend this approach, describing how philosophy differs from science only in being more general and more normative, concerned with how things ought to be as well as how they are.
In contrast, there are many philosophers who think that philosophy and science are fundamentally different enterprises because philosophy can use reason alone, or attention to language and logic, to arrive at truths that are a priori (independent of experience), necessary (true in all possible worlds), or purely conceptual. Unlike these anti-naturalist philosophers, however, I think that Hawking and Mlodinow are justified in trying to look at fundamental questions about the nature of reality by taking into account advances in physics.
The key question is: How well do Hawking and Mlodinow succeed in reaching defensible conclusions about knowledge and reality? Fully answering that question would take a much longer evaluation, but it should be evident from the quotes above that their assertions go well beyond the genuine empirical successes of quantum theory into a realm of philosophical speculation akin to other philosophers who have been skeptical about the independent existence of reality.
The defunct philosopher that Hawking and Mlodinow are unknowingly slaves to is Immanuel Kant, who tried to show that reality is mind-dependent. He was appalled by threats raised by such Enlightenment philosophers as David Hume to his beloved values of religion, immortality, and free will. Kant developed the view that there could be no knowledge of things in themselves because all experience is filtered through schemas. This view is the predecessor of the claim that all knowledge is model-based.
Hawking and Mlodinow repeat the Kantian philosophical error of inferring from the fact that we need minds to develop knowledge of reality to supposing that there is no reality independent of minds and the models they produce. We have abundant evidence from astronomy, cosmology, geology, and biology that human minds are relatively recent additions to the universe, and that stars and galaxies preceded us by billions of years. Minds are needed to construct models of how the universe works, but the workings of the universe do not depend on the relatively recent models that people construct. The relation between minds, models, and reality is an important philosophical problem that arises in many sciences, and contemporary physics alone fails to provide an answer to it.
The philosopher Bertrand Russell and the author Mark Twain are among many people who have been erroneously reported dead and hence were able to read their own premature obituaries. Twain wrote that "the report of my death is an exaggeration." The same is true for philosophy.