Quantum mechanics can sometimes be very hard to understand, so much so that even thinking about it becomes difficult. This could be because its foundations lay in the action-centric depiction of reality that slowly rejected its origins and assumed a thought-centric one garb.
In his 1925 paper on the topic, physicist Werner Heisenberg used only observable quantities to denote physical phenomena. He also pulled up Niels Bohr in that great paper, saying, “It is well known that the formal rules which are used [in Bohr’s 1913 quantum theory] for calculating observable quantities such as the energy of the hydrogen atom may be seriously criticized on the grounds that they contain, as basic elements, relationships between quantities that are apparently unobservable in principle, e.g., position and speed of revolution of the electron.”
A true theory
Because of the uncertainty principle, and other principles like it, quantum mechanics started to develop into a set of theories that could be tested against observations, and that, to physicists, left very little to thought experiments. Put another way, there was nothing a quantum-physicist could think up that couldn’t be proved or disproved experimentally. This way of looking at the world – in philosophy – is called logical positivism.
This made quantum mechanics a true theory of reality, as opposed to a hypothetical, unverifiable one.
However, even before Heisenberg’s paper was published, positivism was starting to be rejected, especially by chemists. An important example was the advent of statistical mechanics and atomism in the early 19th century. Both of them interpreted, without actual physical observations, that if two volumes of hydrogen and one volume of oxygen combined to form water vapor, then a water molecule would have to comprise two atoms of hydrogen and one atom of oxygen.
A logical positivist would have insisted on actually observing the molecule individually, but that was impossible at the time. This insistence on submitting physical proof, thus, played an adverse role in the progress of science by delaying/denying success its due.
As time passed, the failures of positivism started to take hold on quantum mechanics. In a 1926 conversation with Albert Einstein, Heisenberg said, “… we cannot, in fact, observe such a path [of an electron in an atom]; what we actually record are the frequencies of the light radiated by the atom, intensities and transition probabilities, but no actual path.” And since he held that any theory ought only to be a true theory, he concluded that these parameters must feature in the theory, and what it projected, as themselves instead of the unobservable electron path.
This wasn’t the case.
Gaps in our knowledge
Heisenberg’s probe of the granularity of nature led to his distancing from the theory of logical positivism. And Steven Weinberg, physicist and Nobel Laureate, uses just this distancing to harshly argue in a 1994 essay, titled Against Philosophy, that physics has never benefited from the advice of philosophers, and when it does, it’s only to negate the advice of another philosopher – almost suggesting that ‘science is all there is’ by dismissing the aesthetic in favor of the rational.
In doing so, Weinberg doesn’t acknowledge the fact that science and philosophy go hand in hand; what he has done is simply to outline the failure of logical positivism in the advancement of science.
At the simplest, philosophy in various forms guides human thought toward ideals like objective truth and is able to establish their superiority over subjective truths. Philosophy also provides the framework within which we can conceptualize unobservables and contextualize them in observable space-time.
In fact, Weinberg’s conclusion brings to mind an article in Nature News & Comment by Daniel Sarewitz. In the piece, Sarewitz, a physicist, argued that for someone who didn’t really know the physics supporting the Higgs boson, its existence would have to be a matter of faith than one of knowledge. Similarly, for someone who couldn’t translate electronic radiation to ‘mean’ the electron’s path, the latter would have to be a matter of faith or hope, not a bit of knowledge.
A more well-defined example is the theory of quarks and gluons, both of which are particles that haven’t been spotted yet but are believed to exist by the scientific community. The equipment to spot them is yet to be built and will cost hundreds of billions of dollars, and be orders of magnitude more sophisticated than the LHC.
In the meantime, unlike what Weinberg and like what Sarewitz would have you believe, we do rely on philosophical principles, like that of sufficient reasoning (Spinoza 1663, Leibniz 1686), to fill up space-time at levels we can’t yet probe, to guide us toward a direction that we ought to probe after investing money in it.
This is actually no different from a layman going from understanding electric fields to supposedly understanding the Higgs field. At the end of the day, efficient descriptions make the difference.
Exchange of knowledge
This sort of dependence also implies that philosophy draws a lot from science, and uses it to define its own prophecies and shortcomings. We must remember that, while the rise of logical positivism may have shielded physicists from atomism, scientific verification through its hallowed method also did push positivism toward its eventual rejection.
The moral is that scientists must not reject philosophy for its passage through crests and troughs of credence because science also suffers the same passage. What more proof of this do we need than Popper’s and Kuhn’s arguments – irrespective of either of them being true?
Yes, we can’t figure things out with pure thought, and yes, the laws of physics underlying the experiences of our everyday lives are completely known. However, in the search for objective truth – whatever that is – we can’t neglect pure thought until, as Weinberg’s Heisenberg-example itself seems to suggest, we know everything there is to know, until science and philosophy, rather verification-by-observation and conceptualization-by-ideation, have completely and absolutely converged toward the same reality.
Until, in short, we can describe nature continuously instead of discretely.
Liberation of philosophical reasoning
By separating scientific advance from contributions from philosophical knowledge, we are advocating for the ‘professionalization’ of scientific investigation, that it must decidedly lack the attitude-born depth of intuition, which is aesthetic and not rational.
It is against such advocacy that American philosopher Paul Feyerabend voiced vehemently: “The withdrawal of philosophy into a ‘professional’ shell of its own has had disastrous consequences.” He means, in other words, that scientists have become too specialized and are rejecting the useful bits of philosophy.
In his seminal work Against Method (1975), Feyerabend suggested that scientists occasionally subject themselves to methodological anarchism so that they may come up with new ideas, unrestricted by the constraints imposed by the scientific method, freed in fact by the liberation of philosophical reasoning. These new ideas, he suggests, can then be reformulated again and again according to where and how observations fit into it.
In the meantime, the ideas are not born from observations but pure thought that is aided by scientific knowledge from the past. As Wikipedia puts it neatly: “Feyerabend was critical of any guideline that aimed to judge the quality of scientific theories by comparing them to known facts.” These ‘known facts’ are akin to Weinberg’s observables.
So, until the day we can fully resolve nature’s granularity, and assume the objective truth of no reality before that, Pierre-Simon Laplace’s two-century old words should show the way: “We may regard the present state of the universe as the effect of its past and the cause of its future” (An Essay on Probabilities, 1814).
This article, as written by me, originally appeared in The Hindu’s science blog, The Copernican, on June 6, 2013.