My perspective of David Deutsch's The Fabric of Reality -
9January1998
Doug Renselle

 

Revised 13Oct1999. See note 1.

 

To you reader: Note that this is an original review by Renselle. It is four hundred words longer than a review which appears on http://www.amazon.com/.

In The Fabric of Reality David Deutsch chisels his place among new young geniuses entering Millennium III. Humankind shall benefit from his keen intellect, fresh memes, and bold strokes. He prods us and classical legacy-addled physicists to drop our one-universe chauvinism in favor of Hugh Everett's multiverse. Like all humans, though, his greatness complements his imperfection.

Chapter one ends with this ken of Deutsch's personal crux: "I now think that the important issue is not really whether what our particular species understands can be understood by one of its members. It is whether the fabric of reality itself is truly unified and comprehensible. There is every reason to believe that it is. As a child, I merely knew this; now I can explain it."

The Fabric of Reality is about a need to unify four complementary threads: 1) quantum theory, 2) evolution theory, 3) computation theory, and 4) epistemology. Deutsch believes that these four threads are co-synthetics of a theory of everything which leads first time to a "last great unification" making it ultimately possible for an individual quantum-multiverse-supported human intellect to explain everything.

It was not Deutsch's intention, but you may see his four threads as violin strings much like Prince Louis de Broglie's metaphor. Until now, his strings have been in a heap, so to speak, just loosely lying about. But Deutsch offers a framework genesis — a new violin body. You can envision a fledged frame: his new system of thought with four strings carefully strung, tuned and sympathetically united in a resonant violin body. It is up to theorists and technologists to play this instrument, to make more beautiful, harmonious music in this fecund complement of both freedom and confinement.

We see Deutsch's greatness in his stronger points which are: superiority of quantum science, our multiverse as a repository of growing knowledge, a philosophical and scientific failure of inductivism, his proposed use of virtual reality to prototype theories, imminence of quantum computation, his unification of determinism and non-determinism, and his brief but elegant weaving of all four threads.

Rightly, Deutsch calls quantum science our best and most accurate science of reality humankind has at this moment. By comparison, he decries classical and space-time sciences' inaccuracy and diminishing usefulness for Millennium III. He denigrates space-time science as "false," and classical science as "obsolete." Their replacement is a great subsumer: quantum theory and its descendants. We cannot disagree. Bravo!

Appropriately, Deutsch destroys inductivism, positivism, instrumentalism, reductionism, solipsism, and mathematical intuitionism. They are inutile tools for quantum logic. His destruction of inductivism, however germane, appears to rest on his perception: observation is a parent of evil "historical evidence." He rails against historical evidence in his extensive dialogue against inductivism.

From a quantum perspective, his single greatest achievement in his book is not unification of all four threads, but his superb, simple, multiple explanations of interference using pinholes, shadows, multiple slits, and semi-silvered mirrors. His explanations are easy to understand and provide convincing 'explanatory' evidence of our multiverse.

Deutsch, magnificently, and in open defiance of Einstein's general relativity unifies determinism and nondeterminism. He does this by first declaring that all universes in our multiverse are determinate, and second declaring most entities experiences are indeterminate in our multiverse because they make choices. Each entity's choices select different thread segments (snapshots) in its journey through our multiverse. Neat idea, but I worry neo quantum mechanics may find his determinate-universes-in-the-multiverse view still too static and objectivist.

Deutsch's weaker points include a youthful and refreshing arrogance perhaps best depicted by his claim that he can (does) explain physical reality. He puts himself in hot water here by claiming he can put any concept in a framework and then explain it, thus gaining understanding. Later he goes on to say time has no framework, from which you reader must infer it cannot be explained. This seemed to expose a large gap in his framework-explanation method for understanding physical reality.

Too, and unfortunately, Deutsch makes some claims with which I doubt many quantum mechanics would agree, e.g.: "biological variations are random, blind, and purposeless," and, "there is no biological equivalent of argument." This sounds like old, classical stuff. I suspect Brian D. Josephson, in particular, might find these remarks suspect from a quantum biology perspective. One faux pas which left this reader incredulous is his repeated statement, "My bet is that a human brain, considered as a computer, is a classical one [not a quantum one]." Considering a quantum fundamental: quantum systems compose physical reality — his bet appears a likely loser.

Deutsch’s style is nearly stream of consciousness writing. He practices unannounced subtle context switches which are difficult to follow. I was left wanting for lack of multiple, context-managed stack registers to follow most of Deutsch's work. I think he is so smart it is difficult for him to stay at a lower level where most of us reside. It is probably ill-used effort for him to unencumber his context flux for us. We readers just need to get a lot smarter!

Sadly, Deutsch invests incredible time, energy, and space on a dialogue with a crypto-inductivist explaining base inadequacies of inductivism. He goes on to declare himself neither an inductivist nor a crypto-inductivist then boldly manifests his own regressive crypto-crypto-inductivism. Subsequent to this declaration he avers historical evidence and historical frameworks frequently to explain his conclusions. One clear example of his regress-inductivism is his inductive argument against inductivism, "…our present theories say that the future will not resemble the past." Perhaps this is a test to see if we understand his chapter on 'justification.'

Finally I think he carries legacy baggage of classical science's subject-object dichotomy. He throws out classical science, but retains its old umbrella classical metaphysics. I guess this arises from his faith in Popperian philosophy. His four strands are all intellectual patterns of value and thus intrinsically subjective, but he insists on 'justifying' them objectively by giving them 'substance' through explanation in a classical framework. Somewhat redeeming grace, he mitigates classical objectivism's downside via his acknowledgment of his scientific method's provisional nature and his strong (and I believe correct) position on existence of our quantum multiverse (thus admitting multiple frameworks and concomitant multiple truths) which denies classical science’s faulty goal of universal truth.

My big question for David Deutsch is, "Is a reality in which a finite intellect can comprehend everything more real than a reality in which a finite intellect humbly acknowledges there is always more than finite intellect can comprehend?"

To an expectant and careful reader's dismay Deutsch avoids several following topics:

ü Waves (His multiversal interference appears wholly particulate-objective. See Note 1, below.),
ü Complementarity (Probably because a Copenhagen interpretation prefers a single universe.),
ü Superluminality (Deutsch must assume this to achieve zero-latency multiversal interference.),
ü Evolution as a consequence of observation (I.e., Niels Bohr, Copenhagen-like observation. Deutsch sees evolution as a consequence of choices. When one thinks carefully about this, choice is a subsequent to perception which is a subsequent to observation.),
ü Observation as a special event (Deutsch usurps an 'observation' meme with a 'choice' meme.),
ü Context freeness of formal logic as both its major strength and its major weakness, and
ü Whether a classical subject-object dichotomy is a proper framework for physics (Deutsch very blatantly assumes that it is.).

One can only surmise his philosophy denies relevance of these topics in his treatise. His adapted Popperian philosophy appears to contravene relevant artifacts of orthodox Copenhagen quantum theory. I think a unification of Deutsch’s ideas and selected Copenhagen concepts which he dismisses are superior to either alone.

Conclusion: You should read this book. Then ask yourself, "What political motivation won it a Dirac Prize?"

Doug Renselle.

Notes:

Note 1 - Deutsch recently appeared on a PBS science show (CDT 8PM, 12Oct99), and he still sees reality from an objective viewpoint. He and a colleague demonstrated a classical double-slit experiment with multiple photons traversing both slits and (unmeasured) forming familiar interference fringe patterns on a screen. They revise their experiment to only permit successive incremental delivery of unit photons to traverse both slits. One intuits their expectation of a non-fringe particulate spot pattern on a screen (i.e., what we would see if we attempted to measure either or both slits to see which slit a photon object is traversing). However, a familiar interference fringe pattern integrates gradually with each new photon's traversal. Deutsch exclaims, "Since photons are objects our results are impossible unless our individual photons are interfering with photons from other, parallel multiverses."

Here, we see Deutsch still denying photons — and in general, quantum systems — are wavicles. He tells us a photon cannot be in more than "one place, one locus" at a time. He tells us that to make that assumption would be absurd! His simple "one place, one time" statement describes a classical analytical thing. Analytical things (i.e., classical_object = f(t), or in words, classical objects are ideal infinitesimal point functions of time) are innately incapable of interference. 'Orbits' of classical objects decay! Analytical things are incapable of Heisenberg uncertainty (inter)relations. Analytical things are incapable of depicting quantum reality. Analytical things (assuming Einsteinian relativity) are incapable of superluminality, tunneling, etc. All of this argues against an object model capable of interference with itself or, as Deutsch suggests, another multiversal object.

See our review of Irving Stein's, The Concept of Object as the Foundation of Physics.

We are simply amazed! All of quantum science and nearly unlimited and various experiments with various simple quantum systems are interpreted to infer multiversal omnimensionality plus both/and particle/wave nature of all quantum systems. Yet Deutsch tells us that an individual photon, as an objective particle, cannot interfere with itself, but somehow it can interfere with other objective photons both in a local multiverse and in nonlocal multiverses. Did you get that? A photon cannot interfere with self locally, but it can interfere with nonlocal objects in other multiverses!

Bottom line: We still think Deutsch's difficulty is his assumption of an analytic, objective reality. In our opinion, objectivism is a paralytic disease of otherwise great minds. Return