Razor sharp
Proposed by a medieval monk, Occam’s razor
remains the keenest tool for honing our world
view, argues biologist Johnjoe McFadden
O
N MY daily drive into work at the
University of Surrey, I pass a road
sign to Ockham. Perhaps a slight
difference in spelling is one reason why it took
me a surprising while to realise the English
village’s connection to one of the most
fundamental concepts in science – I would
argue, in my now more enlightened state,
perhaps its most fundamental concept.
I am talking about Occam’s razor. The
creation of a 14th-century theologian with
a racy life story, this is a principle often quoted
as “entities should not be multiplied beyond
necessity”. It urges us to choose the simplest
explanations or models for any phenomenon
we observe. If you see moving lights in the
night sky, say, think of known existing entities
such as aeroplanes, satellites or shooting stars
before considering flying saucers.
It has been a tool for scientific progress,
not to mention a guiding principle for our
own thoughts, right up to the present day.
But I believe that modern science has rather
lost sight of the simple fact that simplicity
is the sharpest guide to greater truths.
Ockham is linked to Occam’s razor by
virtue of William of Ockham. Born in the
village around 1285, William went to a
local Franciscan school before being sent
to Oxford to study theology, then known as
“the Queen of Sciences”. This title was largely
due to the influence of Italian theologian
Thomas Aquinas, who had recently
Christianised the work of the greatest
scientist of ancient Greece, Aristotle.
That mind-meld had supplied five scientific
“proofs” of the existence of God, a variety of
metaphysical essences of reality known as
“universals”, and diverse accounts of objects
in terms of their ultimate purpose or telos.
The purpose of acorns was to feed pigs, for
example, while the purpose of pigs was toKIKI^ LJ
UNGfeed humans and the purpose of humans
was to worship God.
Religious scholars of the time were
assiduously dissecting the world into its
plethora of universals, but when William
arrived in Oxford, he was having none of it.
He wielded his razor for the first time as he
claimed these were all entities multiplied
beyond necessity. He went on to insist that
science and religion should never be mixed,
because science is based on reason, whereas
religion derives from faith. He was, I believe,
the first person to so clearly separate science
from its religious tethers, a move crucial to
science’s subsequent secular development.
These weren’t universally popular
innovations. They earned William a charge
of teaching heresy and a summons to be
tried before Pope John XXII in Avignon, in
present-day France. His trial lasted about
four years, but was never completed. William
was forced to flee, chased by a posse of papal
soldiers, after countercharging that the
Pope himself was a heretic. He accepted the
protection of the Holy Roman Emperor Louis
IV of Bavaria, then in bitter dispute with the
Pope, and spent much of the rest of his life
writing what might be interpreted as mildly
snarky treatises about the nature of political
and religious authority.
His razor, meanwhile, acquired many
devotees. Nicolaus Copernicus was one early
adopter. Confronted with the “monstrous”
complexity of the dominant idea that other
astronomical bodies circled our planet, he
declared in his Commentariolus of 1543 that the
planetary motions “could be solved with fewer
and much simpler constructions”. That hunt
for greater simplicity led him to the model
of planets orbiting the sun. Johannes Kepler
later discerned an even greater simplification,
finding three mathematical laws of planetarymotion applicable to all orbiting bodies – laws
later explained in terms of Isaac Newton’s
laws of motion and gravity that were as valid
on Earth as in the heavens. That confirmed
William’s own speculation some 350 years
earlier that “It appears to me... that the matter
in the heavens is of the same kind as the matter
here below. And this is because plurality
should never be posited without necessity.”
The history of science is littered with similar
stories of scientists allowing simplicity to
guide them to greater understanding. But
Occam’s razor seems to have gone rather out70 | New Scientist | 18/25 December 2021