Occam’s razor

Occam’s razor

Photo by Vinicius "amnx" Amano on Unsplash

Originally published 23 July 2006

In the intro­duc­tion to my book Skep­tics and True Believ­ers, I defined two frames of mind:


Skep­tics are chil­dren of the Sci­en­tif­ic Rev­o­lu­tion and the Enlight­en­ment. They are always a lit­tle lost in the vast­ness of the cos­mos, but they trust the abil­i­ty of the human mind to make sense of the world. They accept the evolv­ing nature of truth, and are will­ing to live with a mea­sure of uncer­tain­ty. Their world is col­ored in shades of gray. They tend to be social­ly opti­mistic, cre­ative and con­fi­dent of progress. Since they hold their truths ten­ta­tive­ly, Skep­tics are tol­er­ant of cul­tur­al and reli­gious diver­si­ty. They are more inter­est­ed in refin­ing their own views than in pros­e­ly­tiz­ing oth­ers. If they are the­ists, they wres­tle with their God in a con­tin­u­ing strug­gle of faith. They are often plagued by per­son­al doubts and prone to depression.

True Believ­ers are less con­fi­dent that humans can sort things out for them­selves. They look for help from out­side — from God, spir­its or extrater­res­tri­als. Their world is black and white. They seek sim­ple and cer­tain truths, pro­vid­ed by a source that is more reli­able than the human mind. True Believ­ers pre­fer a uni­verse pro­por­tioned to the human scale. They are repulsed by diver­si­ty, com­fort­ed by dog­ma and respect­ful of author­i­ty. True Believ­ers go out of their way to offer (some­times forcibly admin­is­ter) their truths to oth­ers, con­vinced of the right­eous­ness of their cause. They are like­ly to be “born again,” redeemed by faith, apoc­a­lyp­tic. Although gen­er­al­ly pes­simistic about the state of this world, they are con­fi­dent that some­thing bet­ter lies beyond the grave.


Although indi­vid­ual sci­en­tists might be True Believ­ers, sci­ence can only thrive in an atmos­phere of skep­ti­cism. Sci­ence is open-end­ed; every truth is held ten­ta­tive­ly, sub­ject to change. As Ein­stein once said, the most impor­tant tool of the sci­en­tist is the wastebasket.

So — Skep­tics and True Believ­ers: A gen­er­al­iza­tion, of course, but (I thought as I wrote the book) a use­ful one.

As long as we are gen­er­al­iz­ing, we might also divide our­selves into Occamists or Anti-Occamists.

Let me explain.

William of Occam (c. 1285 – 1347) was an Eng­lish Fran­cis­can fri­ar and philoso­pher, from the vil­lage of Occam in Sur­rey, edu­cat­ed at Lon­don and Oxford, who preached and taught across Europe. He is best know to mod­erns as the author of Occam’s razor, the prin­ci­ple of philo­soph­i­cal par­si­mo­ny: Nev­er sup­pose a com­plex expla­na­tion when a sim­pler expla­na­tion will suffice.

Occam was sure­ly not the first to enun­ci­ate this prin­ci­ple, but he has been assigned the cred­it, and he cer­tain­ly used the prin­ci­ple to great advan­tage, strip­ping away super­flu­ous accre­tions from the phi­los­o­phy and the­ol­o­gy of his time — an exer­cise that earned him excom­mu­ni­ca­tion from from the Church he served.

Occam’s razor is a bedrock prin­ci­ple of mod­ern sci­ence. New­ton put it this way: “We are to admit no more caus­es of nat­ur­al things than such as are both true and suf­fi­cient to explain their appear­ance.” And Ein­stein said: “The grand aim of science…is to cov­er the great­est pos­si­ble num­ber of empir­i­cal facts by log­i­cal deduc­tions from the small­est pos­si­ble num­ber of hypothe­ses of axioms.” Sim­plic­i­ty. Parsimony.

Some­one once quot­ed Shake­speare to the philoso­pher W. V. O. Quine: “There are more things in heav­en and earth than are dreamt of in your phi­los­o­phy.” The remark was meant as a put-down, a sort of “Yeah, what do you know?” To which Quine is said to have respond­ed: “Pos­si­bly, but my con­cern is that there not be more things in my phi­los­o­phy than are in heav­en and earth.” Quine was an Occamist.

On the oth­er hand, I have heard that in an episode of The X‑Files, Fox Mul­der dis­miss­es Occam’s razor by renam­ing it Occam’s Prin­ci­ple of Unimag­i­na­tive Think­ing. Let a thou­sand para­nor­mal and pseu­do­sci­en­tif­ic flow­ers bloom. Mul­der is an Anti-Occamist.

The Occamist does not look for mir­a­cles or the para­nor­mal when a nat­ur­al expla­na­tion will suf­fice. And when no nat­ur­al expla­na­tion presents itself (as, for exam­ple, “What is the source of the sin­gu­lar­i­ty that became the big bang?”) the Occamist is pre­pared to say “I don’t know.” To admit our igno­rance of the prodi­gal­i­ty of cre­ation is not the same thing as to fill our igno­rance with a pletho­ra of gods, spir­its, extrater­res­tri­als, auras, mir­a­cles, mor­phic res­o­nances, astral influ­ences, etc. of our own invention.

Or so we were taught by the poor, brown-robed, san­dal-clad fri­ar from Occam who was a cham­pi­on of intel­lec­tu­al humility.

Occam’s razor, wise­ly applied, has proved a roy­al road to prac­ti­cal, reli­able knowl­edge of the world. Since the time of Galileo, and espe­cial­ly since the Enlight­en­ment, it has been the basis for our health, wealth, and gen­er­al hap­pi­ness. Occam’s razor is our most pow­er­ful tool in the bat­tle against the dark­er demons of sec­tar­i­an strife, reli­gious tri­umphal­ism and pseu­do­sci­en­tif­ic superstition.

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