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A Close Shave from the Past


Lewis Jones

Volume 4.3, September 1994

I wonder how a mid-fourteenth-century Franciscan monk would have felt if he had known that late-twentieth-century magazine readers would vote to give him some aftershave as a Christmas present.

Last Christmas, New Scientist readers came up with suggestions for gifts to famous individuals. Some rubber ducks for Archimedes. A set of dice for Einstein. Protective headgear and a cider press for Newton. The address of a good patent lawyer for Leonardo da Vinci. A cat flap for Schrodinger. A bigger notebook for Fermat.

The aftershave, as you may have guessed, was for William of Occam. The village of Occam, where he was born, was in the southern English county of Surrey; it still is-only a mile or two off the orbital freeway that rings London.

If you come across his name these days, it’s likely to be as part of the term Occam’s Razor: “Entities should not be multiplied without necessity.” To persuade you of its authenticity, the statement often drags in tow the original Latin formulation: “Entia non sunt multiplicanda sine necessitate.” But if you bump into it again, you might find it presented as “Entia non sunt multiplicanda praeter necessitatem.” Yes, you spotted the catch-how can there be two different authentic versions? In fact, there are not two. There isn’t even one. The statement appears nowhere among his extant writings, even though he would probably have agreed with the gist of it.

It was not new. Robert Grosseteste, a chancellor of William’s own university (Oxford) had written: “That is better and more valuable which requires fewer, other circumstance being equal; which necessitates the answering of a smaller number of questions for a perfect demonstration.... As Aristotle says in Book V of the Physics, “Nature operates in the shortest way possible.” And the Franciscans in general leaned heavily on the principle.

William took against the prevailing notion that universals (or abstractions, as we would call them today) existed separately in their own right, apart from individual things. Abstractions, he said, were no more than convenient names. The idea that abstractions should be afloat in the world divorced from objects was, he wrote, “simply false and absurd.”

Then came the step that caused trouble. You could not, he said, find out about the world by just sitting and thinking. Reason alone could prove nothing: you had to deal with things you could observe. It sounds an innocent move in the argument. But its continuation went like this: no one can therefore show that God exists by simply reasoning about it. This was what probably cost William his doctorate at Oxford. The Pope declared him a heretic, and excommunicated him. William compared the papal lifestyle unfavorably with the Franciscan doctrine of absolute poverty and said it was the Pope who was the heretic. Things were never the same again between Pope John the 22nd and “the great iconoclast.”

These days, the Razor is used mostly in the context of discussions about scientific method. It is often said that the Razor means choosing the explanation that is simplest. This is almost always a mistake: the search for the “simplest” is a semantic minefield. Besides, this so-called Law of Parsimony is far from true, as a browse through some of the devious and often wasteful mechanisms of evolution will soon show you. (Divine whim is a much "simpler” explanation of the remnants of a whale’s back legs.) The Razor is most sensibly used to advise against explaining the unknown by inventing things that are themselves unexplained (such as the mental furniture devised to explain the workings of psychoanalysis, or the concoction of “thought waves” to explain claims of telepathy).

In recent years, I've noticed that the Razor has tended to divorce itself from the name of William of Occam and has taken to attaching itself to new partners. Karl Popper (in Conjectures and Refutations) has proposed Berkeley’s Razor-"This razor is sharper than Occam’s: all entities are ruled out except those which are perceived.”

There is also the Liberal Razor-"The state is a necessary evil: its powers are not to be multiplied beyond what is necessary.”

And Popper (in Objective Knowledge) is the only one I have come across who has warned against oversimplifying a complex world by a too enthusiastic use of the Razor: “My point is that only after recognizing the plurality of what there is in the world can we seriously begin to apply Occam’s razor. To invert a beautiful formulation of Quine’s, only if Plato’s beard is sufficiently tough and tangled by many entities, can it be worth our while to use Occam’s razor. That the razor’s edge will be dulled in being used for this tough job is only to be expected. The job will no doubt be painful. But it is all in a day’s work.”

My memory told me that I had come across Hume’s Razor somewhere, but a search through hundreds of pages of philosophical writings failed to reveal it. I finally asked Antony Flew if he could come up with a reference for me. He convinced me that I had simply misremembered, but to fill the vacancy he reminded me of an excellent candidate from Hume’s An Enquiry Concerning Human Understanding: “If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, does it contain any abstract reasoning, concerning quantity or number? No. Does it contain any experimental reasoning, concerning matter of fact or existence? No. Commit it then to the flames, for it can contain nothing but sophistry and illusion.”

Hume’s Razor? Why not? But in all of this, let us not forget to tip our hats in the direction of the fourteenth-century Franciscans, and in particular, William of Occam-the monk who could really cut it.

Lewis Jones

Lewis Jones is a science writer in the U.K.