Re:Paper is a pet project where I get to read interesting papers from the past and share my thoughts/impressions. It's not too dissimilar to book reviews, except for papers. Or paper-like things (a talk that gets published, an essay from an academic etc.)
For 002, we have Carlo Ravolli's Physics Needs Philosophy. Philosophy Needs Physics.
When the ancients on the Indian subcontinent asked and tried to answer, "what is an atom?" and "what does it mean to be indivisible?", we filed them in the Nyaaya-vaiseshika system, one of the six popular philosophical systems of ancient India, because these physical discourses were wrapped in a big dose of philosophy and eventually lead to things like metaphysics and, needless to say, "What is God?" (in a reductive way of speaking).
So it is somewhat crazy that physics and philosophy have drifted apart so much. But it's also quite natural, I think. One had to choose extremities of math and some logic, and the other chose extremities of logic and other means.
What Ravolli speaks of, however, is not the drift in content but in the syncretism that existed between the two. The generous give-and-take because a physicist, say Einstein, did not shy away from immersing in deep philosophy.
We go all the way back to Athenian times when Plato and Isocrates were at logger-heads about their methods of understanding the world at large.
At the time, the golden youth of the city was educated in famous schools. Among these, two stood out: the school of Isocrates, and the Academy, founded by a certain Plato. The rivalry between the two was heated, like the rivalry between Oxford and Cambridge, but was not just about quality: the very approach to education was different in the two schools. Isocrates offered a high-level practical education, teaching the youth of Athens the kind of skills and knowledge required to become politicians, lawyers, judges, architects, and so on. The Academy on the other hand focused rather on discussing general questions about foundations. What is justice? ... What is beauty? What is matter made of? And Plato had invented a good name for this way of posing problems: 'philosophy'.
And Isocrates said of this "philosophy":
Those who do philosophy, who determine the proofs and the arguments … and are accustomed to enquiring, but take part in none of their practical functions, … even if they happen to be capable of handling something, they automatically do it worse, whereas those who have no knowledge of the arguments [of philosophy], if they are trained [in concrete sciences] and have correct opinions, are altogether superior for all practical purposes. Hence for sciences, philosophy is entirely useless
It took Aristotle, student of Plato, to formulate a response to that criticism. Much of that text is unavailable and only collated from other works that quote it.
From that, Ravolli picks three principles:
- ...general theory supports and happens to be useful for the development of practice.
- Those who deny the utility of philosophy, are doing philosophy.
- More in need of philosophy are the sciences "where perplexities are greater".
The meaty part of his paper is spent expanding on the 2nd principle, dipping into Thomas Kuhn and Karl Popper's philosophies of science, scientific revolutions and the methodologies that should be employed by science. This is, in my opinion, the most interesting part of the paper.
In the post-quantum world, there is far less attraction to philosophy and the philosophical toolkit than there was in Einstein's era and before. Ravolli quotes Weinstein and deGrasse Tyson as having much disdain for philosophy (in the context of how useful it is for physics). This is perhaps an echo of the Vienna Circle where logical positivism was born, beginning the removal of some (or all) aspects of philosophy from the act of doing hard science.
But we are to remember that the Heisenbergs and Einsteins of the world frequently credited philosophy for their inspiration:
Both major advances made by twentieth century physics were strongly influenced by philosophy. They would have been inconceivable without the philosophy of the time.
Quantum mechanics springs from an intuition due to Heisenberg, grounded in the strongly positivist philosophical atmosphere in which he found himself: one gets knowledge by restricting oneself to what is observable. ...
... by restricting to what is observable, we recognise that the notion of simultaneity is misleading. Einstein explicitly recognised his debt to the philosophical writings of Mach and Poincaré.
...Once again, he [Einstein] was explicit in recognising his debt to philosophy, this time to the critical thinking of Leibniz, Berkeley, and Mach.
And going back, Newtons and Galileos too. I particularly liked the notion that Galileo's findings came about from his "almost fanatic Platonism" of search for ideal mathematical order underlying observed phenomena.
Ancient astronomy—that is, everything we know about the Earth being round, its size, the size of the moon and the sun… , is a direct descendent of philosophy.
Galileo's work would have been inconceivable without the ideology he derived from Plato, namely, to search for the ideal mathematical order underlying appearances. Galileo was guided by an almost fanatic Platonism. In his work, Newton was explicit about his debt to ancient philosophy, Democritus in particular, for ideas that arose originally from philosophical motivations, such as the notions of empty space, atomism, and natural rectilinear motion. Furthermore, his crucial discussion about the nature of space and time built upon his discussions with (and against) Descartes.
If you think about it, in some sense, philosophical discourse about reductionism and an order of rules (laws or axioms) governing all phenomena is the spiritual thrust for a bunch of physics nirvanas being searched for earnestly, all the way from a unifying theory for quantum and gravity to supersymmetry and such. (Which, I understand, is also an argument that could go against being influenced by philosophy!)
The core idea that Ravolli is after is that physics (or science) can sometimes lack the tools at such advanced levels of functioning, at crossroads, and at times when a breakthrough is needed.
philosophy can provide methods for producing new ideas, novel perspectives, and critical thinking. Philosophers have tools and skills that physics needs, but do not belong to the physicists training: conceptual analysis, attention to ambiguity, accuracy of expression, the ability to detect gaps in standard arguments, to devise radically new perspectives, to spot conceptual weak points, and to seek out alternative conceptual explanations.
Physics has engaged in/with philosophy at almost all times. Even when Weinberg or Hawking write dismissively about philosophy, Ravolli contends like Aristotle that they're doing philosophy.
Good scientists do reflect on their own methodology...
and when Kuhn or Popper talk about science and revolutions in it:
They express a certain idea about the methodology of science. Is this the eternal truth about how science has always worked and should work? Is it the best understanding of science we have at present? It is neither. In fact, it is not difficult to trace the origins of this idea. It arises from the background of logical positivism, corrected by Popper and Kuhn. The current dominant methodological ideology in theoretical physics derives from their notions of falsifiability and scientific revolution, which are popular among theoretical physicists; they are often mentioned and are commonly used to orient research and evaluate scientific work.
I liked this bit about how physics almost always has had an evolving soul of conceptual structures and reflectiveness. This is, in some sense, what philosophy is about.
…conceptual structures evolve as well. Science is not simply an increasing body of empirical information we have about the world and a sequence of changing theories… evolution of our own conceptual structure… the modification of the conceptual structure needs to be achieved from within our own thinking…
…intertwining of learning and conceptual change, this flexibility, and this evolution of methodology and objectives, have developed historically in a constant dialogue between practical science and philosophical reflection…
And back to the tools:
(Quoting Aristotle) "Philosophy provides guidance how research must be done."
... Not because philosophy can offer a final word about the right methodology of science (contrary to the philosophical stance of Weinberg and Hawking). But because philosophers have conceptual tools for addressing the issues raised by this continuous conceptual shift.
Before I write about the part where Ravolli dives deep into how we have misinterpreted (or rather, interpreted at face-value) Kuhn and Popper, let's revisit what these two folks had to say which has influenced generations since.
Please hold simultaneously the thought that this is a layman's reduction of complex ideas put forth by Kuhn and Popper.
On discontinuity: Kuhn effectively says that revolutionary ideas in science do not come from a continuous lineage of cumulative ideas and theories. There are discontinuities where paradigm shifts happen. Think Einstein's leap into general relativity from Laplace or Newtonian laws of motion.
On falsifiability: Popper turned the logical positivism that stemmed from Vienna Circle and said, "seeing only white swans does not prove there are no black swans." Theories can only be proved false, not true.
Ravolli on Kuhn and discontinuity:
Kuhn's emphasis on discontinuity and incommensurability has misled many theoretical and experimental physicists into disvaluing the formidable cumulative aspects of scientific knowledge. Popper's emphasis on falsifiability, originally a demarcation criterion, has been flatly misinterpreted as an evaluation criterion. The combination of the two … has given rise to disastrous methodological confusion: the idea that past knowledge is irrelevant when searching for new theories, that all unproven ideas are equally interesting and all unmeasured effects are equally likely to occur, and that … the work of a theoretician consists in pulling arbitrary possibilities out of the blue and developing them, since anything that has not yet been falsified might in fact be right. … "why not?" ideology: any new idea deserves to be studied, just because it has not yet been falsified; any idea is equally probable, because a step further ahead on the knowledge trail there may be a Kuhnian discontinuity that was not predictable on the basis of past knowledge; any experiment is equally interesting, provided it tests something as yet untested. … think that this methodological philosophy has given rise to mountains of useless theoretical work in physics and many useless experimental investments.
I love this bit on how some of the most radical shifts has come about from an overwhelming amount of data that questions the accumulated knowledge so far or pre-existing contradictions in prevalent theories of the day, thereby positing that stuff just doesn't jump, it in fact follows from existing work of the past:
The most radical conceptual shifts and the most unconventional ideas that have actually worked have in fact always been strictly motivated, almost forced, either by the overwhelming weight of new data, or by a well-informed analysis of the internal contradictions within existing, successful theories. Science works through continuity, not discontinuity. … Kepler did not just "come out with the idea" of ellipses: nature had to splash ellipses on his face before he could see them. He was using ellipses as an approximation for the deferent-epicycle motion of Mars and was astonished to find that the approximation worked better than his model … atomic physicists of the early twentieth century struggled long and hard against the idea of discontinuities in the basic laws, doing everything they could to avoid accepting the clear message from spectroscopy, that is, that there was actually discontinuity in the very heart of mechanics. In both instances, the important new idea was forced by data.
Overwhelming data and Kepler:
Kepler did not just "come out with the idea" of ellipses: nature had to splash ellipses on his face before he could see them. He was using ellipses as an approximation for the deferent-epicycle motion of Mars and was astonished to find that the approximation worked better than his model … atomic physicists of the early twentieth century struggled long and hard against the idea of discontinuities in the basic laws, doing everything they could to avoid accepting the clear message from spectroscopy, that is, that there was actually discontinuity in the very heart of mechanics. In both instances, the important new idea was forced by data.
Contradictions in existing theories and Copernicus and Einstein:
… second case—radical novelty from old theories—are the heliocentric system and general relativity. Neither Copernicus nor Einstein relied significantly on new data. But neither did their ideas come out of the blue. They both started from an insightful analysis of successful well-established theories: Ptolemaic astronomy, Newtonian gravity, and special relativity. The contradictions and unexplained coincidences they found in these would open the way to a new conceptualisation.
On Popper's falsifiability, Ravolli tries something that I found quirky. He tries to kick the puck back into the realm of logical positivism (although, not exactly, and it's nuanced) even though that's the circle that rejected philosophy.
… emphasis on falsifiability has made physicists blind to a fundamental aspect of scientific knowledge: the fact that credibility has degrees and that reliability can be extremely high, even when it is not absolute certainty. … failing to see that a given investigation may have little plausibility even if it has not yet been falsified.
Remember Aristotle and his "More in need of philosophy are the sciences 'where perplexities are greater'"?
Here is a list of topics currently discussed in theoretical physics: What is space? What is time? What is the "present"? Is the world deterministic? Do we need to take the observer into account to describe nature? Is physics better formulated in terms of a "reality" or in terms of "what we observe", or is there a third option? What is the quantum wave function? What exactly does "emergence" mean? Does a theory of the totality of the universe make sense? Does it make sense to think that physical laws themselves might evolve? It is clear to me that input from past and current philosophical thinking cannot be disregarded in addressing these topics.
In loop quantum gravity, my own technical area, Newtonian space and time are reinterpreted as a manifestation of something which is granular, probabilistic, and fluctuating in a quantum sense. Space, time, particles, and fields get fused into a single entity: a quantum field that does not live in space or time. The variables of this field acquire definiteness only in interactions between subsystems. The fundamental equations of the theory have no explicit space or time variables. Geometry appears only in approximations. Objects exist within approximations. Realism is tempered by a strong dose of relationalism. I think we physicists need to discuss with philosophers, because I think we need help in making sense of all this.
Ravolli spends the last couple of paragraphs trying to connect the other way round - philosophy needs physics too - but it's as if Ravolli thinks that self-evident and needs not much of a convincing:
No great philosopher of the past would ever have thought for a moment of not taking seriously the knowledge of the world offered by the science of their times. …
Our general knowledge is the result of the contributions from vastly different domains, from science to philosophy, all the way to literature and the arts, and our capacity to integrate them.