When Mano Singham announced that he was retiring early in order to make time for the book he was writing, many of his colleagues were dismayed. He had been a legendary teacher. What a waste of his talents it would be to quit teaching! And hadn't he already written three fine books? What was the need for another?

We now have the answer to that question. The book that Singham had in mind was to be the most important and valuable of them all, for it is a deep and thoughtful attack on the fundamental issue of how science works. I use the word “attack” deliberately, for the central theme of his book is a devaluation of the concept of truth. As he puts it in his closing words (emphasis in the original),

Truth and correspondence with reality are unnecessary as explanatory concepts in science and …. we can regard them as irrelevant and can comfortably dispense with them as no longer serving any useful purpose.

These are fighting words indeed, and they require the persuasive support of the careful and detailed arguments that form the bulk of this valuable book. The writing is clear and direct and is tailored to an audience that does not necessarily have any science training.

Singham begins by reminding us that our bodies have poorly equipped us to observe the world around us, so that the era of modern science only began with the invention of telescopes and microscopes. Scientific discovery does not occur as a linear process but follows many unproductive pathways before a consensus is reached. History tends to ignore the unsuccessful approaches and over-simplify the way science advances. The text-book stories of discoveries, we are told, should be treated with skepticism. This brought to my mind the accounts given by Einstein, late in his life, that he had conceived the theory of relativity as a necessary logical construct in the absence of any knowledge of the Michelson–Morley experiment, a claim that has been challenged by scholars of his early correspondence with his future wife.

With these first doubts about the nature of scientific progress duly sown, the author now makes his first sortie in the softening-up process to weaken our confidence in the usefulness of the word “truth.” Scientists, we are told, are principally concerned with “what works.” Theories that don't work are discarded. Constructs like phlogiston and the luminiferous aether are replaced with those that are more useful, but it is not necessary to categorize the new ideas as truth. The question as to why a theory works is subordinate to the question of the boundaries of where it works. Chapter 6 of the book is a masterfully crafted account of how scientific opinion about the age of the Earth has developed, and this forms the basis of an instructive analysis in Chapter 7. The conclusion is that the accepted answer to any scientific question is not immutable but is subject to constant refinement and modification, and this fact does not diminish the validity of the scientific process in any way.

From this vantage point, Singham leads us into a discussion of the concept of falsification. After reminding us of Popper's dictum that no scientific theory can be proved to be true, he shows us the weaknesses in the proposition that theories can be proved to be false. He cites examples of observations that were at variance with several well-accepted theories, starting with planetary orbits that violated Newton's laws and continuing through to the apparent, but mistaken, detection of sub-atomic particles outside the well-accepted Standard Model. He also points out that interpretations of experiments that challenge particular theories generally rely on assumptions derived from other theories, and so it is not apparent which theory has been falsified. Is some reliance on “good sense” necessary?

At this point, Singham makes an analogy between scientific conclusions and those of the legal system. I at first found this offensive; we scientists are working to understand better the eternal structure of the natural world, while legal systems are clumsy constructs designed to achieve political ends, often with evil intent. My indignation was quelled, however, as he made the point that, in ideal circumstances, both rely only on a preponderance of evidence to reach their conclusions. In the absence of axioms, we cannot prove a statement to be true, but we can be confident in our conclusions.

As a description of how science works, this is a fair statement when “science” is treated as a single unified field of activity with a well-defined boundary but with no significant internal divisions. It is in sharp contrast to Philip W. Anderson's seminal 1972 discussion More is Different, in which he rescued the concept of axioms in science. Anderson posited the hierarchical structure of science as particle physics – many-body physics – chemistry – molecular biology – cell biology – ⋯ – psychology – social sciences, with each successive level in the hierarchy taking the accepted results of the previous level as axiomatic.

Singham develops his theory further in analogy to Darwin's “Tree of Life” with the concept of a “Tree of Scientific Paradigms.” Physics, chemistry, and biology, we are told, are “separated by largely unbridgeable gaps, just like humans and dogs and sharks on the biological evolutionary tree.” He then extends this analogy to suggest that the many possible paths that evolution might have taken are mirrored in the development of science, which could have followed any of several completely different pathways, leading to a set of scientific theories looking nothing like what we have now. “Thus the parallel between scientific progress and biological evolution” we are told, “is complete, ….” Again, this raises more questions about the structure of science and its subdivisions. Readers, especially if they are biophysicists, may wonder whether physics and biology are really unbridgeably separated; could some branches of the tree not have fused together again?

The core of the book's argument comes with a further tree metaphor, the “Tree of Science,” in which the branches at each level represent different possibilities for all of scientific knowledge at a particular time. As time passes, the different branches fork to produce more and more possible assemblies of knowledge and concepts. The key idea is that all these branches have equal validity, and so there is no unique pathway, and thus no unique scientific truth. We happen to have followed one particular route among the many paths not taken. This novel proposition is in contrast to the commonly prevailing opinion that there is a single correct view of how the universe works, and that although we can never reach the goal of complete understanding, science is making steady progress towards a better and better grasp of the total picture. The traditional view has the tree upside down with disparate views gradually merging on their way to a more complete understanding.

Singham's final chapter persuasively elaborates his thesis that there is no unique scientific truth. He may not succeed in persuading all of us that the Holy Grail we have been seeking is only a chimera, but we will all be stimulated to question our assumptions in many ways as he leads us on his journey. He deserves our whole-hearted thanks for challenging us to confront our previous assumptions, and for doing so by means of such a thoroughly enjoyable and readable book.

Philip L. Taylor is an Emeritus Professor of Physics at Case Western University. His published books include Condensed Matter Physics (co-authored with Olle Heinonen, Cambridge University Press, 2002) and The Sunken Restaurant (ATBOSH Media, Limited, 2019). The latter book is shorter, funnier, and less expensive than the former.