Dear Dr. Harris:
At one point in your comments to Dr. Chopra (in “The Future of God” debate), you stated that one will never see a theoretical physicist make a categorical, dogmatic assertion. But I have often seen physicists (and philosophers of physics) do just that. One example is the often-dogmatic assertion that ‘physics implies a block world’ (i.e. that the future exists just as the past and present), when in fact physical theory does not force that conclusion (see, e.g., Raphael Sorkin’s “Relativity does not imply that the future already exists”).
A famous historical example of a baldly dogmatic statement by a theoretical physicist is Niels Bohr’s categorical assertion: “There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature…” (as told to Aage Petersen; my emphasis). Now, Bohr had certainly done some careful philosophical investigation into quantum theory, and there are many subtleties to his thought and much that can be debated about his philosophical approach. But his explicitly dogmatic assertion about what constitutes ‘wrong thinking’ is neither scientifically nor philosophically justified. It presumes certain metaphysical and epistemological tenets that can be, and have been, rationally questioned. For example, Bohr presumed that everything about the physical world must be describable in classical terms. But in fact one can take quantum theory’s mathematical formalism as providing real information about the structure of the quantum world, even though we cannot capture that structure in the usual classical language of ordinary experience.
So unfortunately scientific researchers often deal with unresolved interpretational aspects of physical theory by lapsing into dogma. Contra Bohr, there certainly can be a quantum world, and physical theory certainly can be saying something about its nature, even if that nature is non-classical. Bohr’s assertion presupposes a conceptual and linguistic framework that is not essential or necessarily appropriate to the task at hand. In more colloquial terms, he was thinking inside a particular kind of box, and his dogmatic pronouncement sought to impose that box on all other researchers. This is why the Irish physicist John Bell railed against Bohr’s unjustified circumscription on discourse, writing a now-famous paper entitled “Speakable and Unspeakable in Quantum Mechanics”.
Of course, quantum theory certainly presents science with a wholly new kind of interpretational dilemma, since its formalism inhabits a domain mathematically larger than that of the empirical (3+1 spacetime) realm that is the traditional domain of physical science. My own proposed resolution to this dilemma involves a rationally grounded step beyond the empirical realm. That is, I offer the view that QM is a physical theory whose referent is a kind of reality that cannot be empirically observed. While this may seem radical, it should be kept in mind that Ludwig Boltzmann took a similar step when he proposed unobservable ‘atoms’ whose behavior gave rise to the macroscopic laws of thermodynamics. Though derided by his contemporaries (in particular Ernst Mach), Boltzmann’s postulation of unobservable entities turned out to be the fruitful way to go. (While we think we ‘observe’ atoms now, we actually just indirectly image them; those images are the results of particular kinds of interactions with our macroscopic instruments.)
The point here is that not all of reality describable by physical theory is necessarily contained within the empirical realm, even though physical theories can only be tested by checking against empirical data. There is no necessary logical incompatibility between these two circumstances. Indeed there are often good theoretical reasons (such as the predictive successes of theories based on unobservables) to allow for the existence of unobservables.
This naturally brings us to the topic of spirituality, which was the main subject of the debate. This feature of human experience (that is, at least of many humans) was unfortunately trivialized in the discussion by an assertion that modern monotheistic schools of thought are substantially the same as ancient worship of polytheistic gods. But in fact there are deep and significant differences between, say, Christian monotheism and worship of the Greek pantheon. I don’t think one will find a Zeus-worshiper saying things like “Show by your good life that your works are done with gentleness born of wisdom…the wisdom from above is first pure, then peaceable, gentle, willing to yield, full of mercy and good fruits, without a trace of partiality or hypocrisy…” (James 3:13, 17; New Testament)
In any case, it is perfectly possible that spiritual experience–which is primarily subjective and inward in nature–is simply a different mode of knowledge and discovery complementary to the scientific mode, the latter being primarily intersubjective and based on outer sensory experience. Thus, spiritual experience might just be another way that many people ‘intuit’ the existence of sub-empirical aspects of the world. This is why it could make sense for the hermit in the cave to have an inner experience of an ‘unseen’ aspect to reality that could just possibly be the same reality described by quantum theory. Note that this suggestion is not dogma, just an offer of a possible connection between science and spirituality. In fact other researchers have suggested such a connection–e.g., Fritjof Capra (The Tao of Physics) and Gary Zukav (The Dancing Wu Li Masters). That is why I found it unfortunate to see such a schism between religion and science evidenced in the Caltech discussion, when in fact there may be some common ground between these different ways of knowing.
You and Dr. Shermer are right that organized religion has been a cause of much evil and suffering–and in fact that seemed to be your primary concern about religion in the debate. But all modes of knowledge can be abused for destructive purposes. Many wars are fought not over religion but to serve geopolitical and territorial goals, with religious or other lofty ideological principles (e.g., ‘freedom and democracy’) often being used as a pretext for conquest and domination. Many scientific discoveries were ‘spinoffs’ of inquiries into how to be more effective in war (for example, the kinematics of projectile motion was a byproduct of efforts to improve cannonball aim).
Finally, to return to the concern that opened this letter: the temptation to overstate one’s case and be dogmatic is not confined to those professing claims about spiritual knowledge. It is an ever-present trap for all researchers to fall into, and those in the ‘rational’ knowledge traditions, including the sciences, are not immune.
P.S. Regarding free will, which you have apparently ruled out: it is certainly not a foregone conclusion that physical science disallows robust free will. That assertion, which is well on its way to becoming a dogma itself, is based either on not taking quantum theory into account or on a particular use of the quantum probability law that arguably is not justified. See, for example my earlier post:
 The Genius of Science: A Portrait Gallery (2000) by Abraham Pais, p. 24
I use the word ‘intersubjective’ rather than ‘objective’ here, because no individual scientist can get outside his or her perceptions to perceive an independently existing reality, but must rely on corroborations between many individual reports. If this seems like nitpicking, one might wish to read Chapter 1 of Bertrand Russell’s The Problems of Philosophy, which points out in graphic detail how no two people ever really see the same table, and moreover that it is a highly nontrivial question as to whether there even is a ‘real,’ objective table independently of observation.
 If I’m ever found to have committed such a lapse, I will readily acknowledge and correct it.