While most accounts of the development of science begin with the Greeks and pay little attention to medieval writers, Johnjoe McFadden accords the central role to a 14th-century Franciscan friar, William of Ockham.

Ockham’s significance is seen principally in his articulation of what became known as Occam’s razor, often rendered as “entities should not be multiplied beyond necessity”. This principle of parsimony has frequently been utilised by scientists in arguing for the strength of their theories against more complex alternatives. Other aspects of Ockham’s philosophy likewise appeal to McFadden, who is also clearly attracted to him because of his antipathy towards papal authority.

Taking Occam’s razor as a tool to simplify scientific theorising, McFadden traces its importance in subsequent history. Thus, Copernicus, Kepler, Galileo, Boyle, Newton, Kelvin and Einstein are all portrayed as employing the razor to aid the progress of science. However, McFadden weaponises Occam’s razor, creating an overly sharp distinction between heroes and villains, even chastising some of the aforementioned scientists for their commitment to allegedly less acceptable philosophies of nature.

In adopting this Whiggish approach, the author makes Ockham’s views appear too modern and, therefore, anachronistic, while condemning all aspects of history that do not cohere with his own prescription. For example, despite many historians having shed considerable light on the practice of alchemy, McFadden firmly asserts that it is nonsense. Likewise, he rejects any role for religion in science as an unacceptable complication, despite the fact that many of his heroes, listed above, conceived the physical world as God’s creation and framed their science accordingly.

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While alchemy and religion are easy targets, McFadden’s account also oversimplifies – and thus distorts – science as a whole. For example, his dismissal of ethereal fluids as superfluous to science ignores the considerable literature of the 18th and 19th centuries that drew on Newton’s speculation, in later editions of his Opticks, that space is pervaded by a rare, elastic “Æthereal Medium”. Theorising about the role of this ether was a highly creative activity that initiated many significant experiments and ideas, including Thomas Young’s wave theory of light. More important in the present context, ethers were often evoked to link diverse phenomena and unify different fields of science. Thus, far from being inimical to simplicity, ethereal fluids played a significant role in simplifying science.

While initially focusing on Occam’s razor, McFadden subsequently discusses other forms of simplification in science, including the framing of laws that summarise a body of observations and statements correlating observations. Yet if he had applied this weaker criterion consistently, he would have included Aristotle, Ptolemy and Galen among his heroes and not disparaged them as anti-scientific for failing the razor test.

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Rather surprisingly, the chapter on evolution is principally concerned with a paper by its co-discoverer Alfred Russel Wallace (perhaps because McFadden seems to be attracted to social outsiders), with Darwin relegated to the sidelines. The lengthy discussion of Wallace’s travels and tribulations adds little to the reader’s understanding of simplicity.

Despite these shortcomings, McFadden includes much interesting material drawn from Ockham and other historical sources. His evident enthusiasm for his subject is particularly welcome as this book is directed not only at fellow scientists but also at a wider readership.

Geoffrey Cantor is professor emeritus of the history of science at the University of Leeds.

Life Is Simple: How Occam’s Razor Set Science Free and Unlocked the Universe
By Johnjoe McFadden
Basic Books, 384pp, £25.00
ISBN 9781529364934
2 September 2021

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