Hase Occam's Razor ever been scientifically verified?

We skeptics love to quote “Occam’s Razor” (i.e., that entities should not be multiplied unnecessarily, or the simplist solution is usually the correct one).

Occam’s Razor means that the strange lights in the sky are NOT likely to be interstellar craft piloted by little green men, since that explanation requires many additional assumptions and there are other much easier explanations.

Similarly, Occam’s Razor means that crop circles are likely NOT caused by “plasma vortices” or the aformentioned little green men, since, once again, those explanations require many additional assumptions whereas the theory that crop circles are made by pranksters with ropes and boards doesn’t.

My question is whether anybody has applied the scientific method to Occam’s Razor itself to test whether it is actually a valid principle or not? Did William of Occam come up with this principle after careful observation, or was it just something he came up with off the top of his head? Has anybody studied large sets of data to determine whether the simplest explanation actually tends to be the correct one more often than not? And, if so, how often does the simplest explanation turn out to be the correct one (in other words, does “more often than not” mean 55% of the time, or close to 100%, or what)?

In short, how do we know that Occam’s Razor is a valid principle, and to what degree are there exceptions to the general rule?



Occam’s razor is a decision procedure, not a proposition, and is therefore not subject to experimental verification.

OK, but how do we know it is a valid procedure? Have any studies been done to show whether following this procedure yields significantly better results than not following it?

It’s easy to debunk a theory by stating that “Occam’s Razor indicates that this theory is likely incorrect,” but what justifies us in relying on Occam’s Razor in the first place?


The thing that justifies using Occam’s Razor is saving time and resources. It doesn’t necessarily mean that the simpler solution will be correct, just that by testing the simpler solution first, if it is wrong, we can rule it out and move to the next simplest possibility.

Yeah, what Xray said.

It’s just a way of deciding which hypothesis to test first, not which one is more correct.

Xray (and SimonX), that’s not what most people mean when they invoke Occam’s Razor. Usually, if there are two possible explanations, one being simple and the other requiring bizarre conditions, Occam says that, until further evidence comes in, it’s best to assume the simple one is correct over the complex one.

I think it’s just a way of restating things, because implicit in the idea that there is a simple explanation is that it’s fairly likely, while complex ones require several unlikely conditions be compounded together. Whether it’s right or not depends on the individual circumstances.

[And, just in case anybody is wondering, the title of this thread should have read “Has Occam’s Razor ever been scientifically verified?” Occam’s first name was, in fact, William and not “Hase”…]

Occam’s razor can’t be scientifically verified because it can’t be falsified. It is, however, still a useful principle specifically because it does lead one to start with the more easily falsifiable explanations first.

I disagree. Occam’s Razor does tell us which hypothosis to test first, but there is more to it than that. It defines, from a certain philodophical perspective, what it means to explain something. In a sense, it defines what it means to say that an explanation is correct. For example, if we know that there are pranksters with wooden boards and rope, and that these pranksters produce crop circles, Occam’s Razor tells us that our work is done–we have explained crop circles. It doesn’t matter whether energy vortices or aliens exist, because we already have an explanation for crop circles that doesn’t require them. If we discover a crop cricle that we know was NOT caused by pranksters with wooden boards and rope, then we have new evidence and hence a new situation calling for a new hypothosis. There are an infinite number of unobserved phenomena that could be posed as ad hoc explanations for crop circles (faries, ghosts, angels, Cthulu, black helecopters, etc.), but Occam’s razor tells us that unless we NEED to posit the existance of those things to explain crop circles, crop circles are not evidence for their existance. In a sense, Occam’s Razor is mathematically provable–the probability that at least some crop circles are caused by pranksters is 1. The probability that at least some crop circles are caused by pranksters, but others are caused by something else is necessarily less than 1.

There are other ways of understanding the world, however. The Roman Catholic Church, to use one example, does not disagree with Occam’s Razor as a principle of science, but it has a different understanding of explanation than science does. A scientist (following Occam’s Razor) would say that if we know that life exhibits natural variation and that nature places selective pressures on those variations, causing life over several generations to respond adaptively, than our work is done–we have explained the varous forms of life found on the planet. The Catholic Church agrees with everything except the completeness of the explanation–we have not fully explained the origin of species until we have explained how evolution expresses God’s will. (In technical terms, they retain the category of final causation, which science does not.) One is not more or less valid than the other, they just ask different questions.

Occam’s Razor is indeed used as a pruning method, and it does define certain kind of standard for the notion of a complete explanation. It does not presuppose that the Universe is simple, just that the scientist’s job is to search for the simple explanations first. If it can be shown that the simple explanations are incomplete, then we can proceed stepwise up the complexity ladder until we find the simplest possible complete explanation.

How do we verify it? We don’t, really. At least, we can’t prove it like we can prove the Pythagorean Theorem or the Quadratic Equation. Nor can we prove gravity or cellular respiration, for that matter. We can’t derive it from first principles because it forms a first principle. We can only observe that it has served us very well in the past, that to abandon it would lead to chaos, and that it doesn’t seem to be failing.

If that doesn’t satisfy, prove that your mind is a useful tool in determining how useful something is.

Occam’s razor can be shown to make sense mathematically, if that works for you.

Assume ALL unproven assumptions are equally likely, say 80% likely.

Aliens making crop circles requires that we assume that A) aliens exist, and B) aliens make crop circles.

That requires 2 80% chances, or .8 * .8 = 64% chance.

Meanwhile, we know that people exist, so, we only need to assume that people make crop circles, 80%.

80% > 64%, so it’s more likely that it’s people.

Granted, some assumptions aren’t as likely as others, but for MOST ways of deducing, something is more likely to be true if it involves less wild ass guesses, and more facts.

I think this is exactly what godzillatemple is asking. Has anyone ever made this observation in an unbiased manner?

Not necessarily true. All eyewitness accounts of the existence of people come from Earth-born beings that themselves claim to be “people”. To this date, not a single other living being has officially claimed that people exist - not dogs, not giraffes, not even bacteria. On the other hand, Earth-born beings, who, it would appear, are not aliens, have come forward with numerous claims of the existence of aliens.
Hence, despite the admitted untrustworthiness of the vast majority of eyewitnesses for the existence of alien life forms, it seems clear that it is more likely that aliens from another planet came to planet Earth and made crop circles than that “people” from planet Earth made the circles.

But if and when the evidence in support of the bizarre possibility comes in, it automatically becomes the simpler explanation (in as far as simplicity can be usefully defined here as the solution that contains the least number of unknown factors)

I disagree that Occam’s (or Ockham’s) Razor is a scientific law, or can be reduced to percentages, or that it provides a structure for deciding which hypotheses to test first based on simplicity.

Rather, I would assert that it is a principle of clear thinking: It forces you to objectively evaluate exactly what you have evidence for, and what you are lacking, and thereby determine which hypotheses are worth considering further. Not first: but either/or.

In the case of the crop circles, we have basic physical evidence, and we have a bunch of guys who have proved they’ve made a bunch of circles using physical means. We have nothing else.

In the absence of radiological or genetic data to support alternate hypotheses, the evidence suggests we should look for a simple explanation, one that doesn’t depend on evidence we don’t possess and cannot reliably speculate about. We have such an explanation. We should therefore put more weight on it.

If we had other physical evidence (e.g., we know that every now and then a helicopter pilot loses control, plunges to earth upside-down, then slows and stops two feet above the earth, before flying safely onward, and we know that these helicopter incidents have been reported in the same areas that crop circles are later spotted), we could apply that evidence to formulate another reasonable hypothesis. Or if we came into possession of beyond-physical evidence (e.g., ten years after a crop circle is formed, the stalks of grain thus manipulated acquire sentience and ambulation and storm the center court at Wimbledom), we could introduce another possible hypothesis. In the absence of that evidence, however, it is unwise to pursue what cannot be reasonably evaluated.

The famous example from scientific history in which Occam’s Razor proved ostensibly misleading is in plate tectonics. Looking at a map, it seems obvious that the coasts of Africa and South America match together like puzzle pieces. But without any mechanism to explain how they separated from one another, it is perfectly reasonable to dismiss the idea as a coincidence. Alfred Wegener began amassing evidence in support of continental drift, but it was insufficient to convince the establishment, and he died before his ideas were validated. However, once the accumulated evidence was undeniable, plate tectonics went from fringe radicalism to established orthodoxy in a virtual eyeblink. Occam’s Razor, in other words, cuts both ways: You may well be right, but until you have the proof it doesn’t matter. This, it seems to me, is an eminently worthwhile philosophical guideline.

I’m not sure it can even be stated explicitly - I would have said which explanation is a subjective matter.

Being correct in the past doesn’t help. Why should we assume that just because it used to work it’ll go on working? How do we choose between the hypotheses that “Occam’s Razor always works,” and “Occam’s Razor works until 2005, and in odd years thereafter,” among others? We can’t use Occam, as that’s what we’re trying to prove.

(However, I suppose it would be possible for Occam’s Razor to be prooved wrong if more complicated explanations were consistantly preferred.)

I think it’s more of an axiom than anything else, and one so basic that we only notice it when someone breaks it. When I say “so so-and-so by Occam’s Razor,” what I mean is “I choose this hypothesis on the basis of Occam’s Razor. If you choose differently, I don’t think we can communicate meaningfully, so I’ll just stop the discussion here.”

Indeed. I’m just a little long winded is all.

Occam stated that the simplest explanation is most likely the correct one. What justified him in stating this? What justifies us in believing this? Are there examples where people were looking for an explanation of an unknown phenomenon, applied Occam’s Razor to select the simplest explanation, and later discovered that this was, in fact, the correct explanation? How about the converse: are there known cases where the simplest explanation turned out to not be the correct one?


On a more technical note, in certain specialised fields of data mining, Occam’s razor has been proved to be incorrect. However, this has little real applicability to the real world problem.

cite: http://www.avcc.edu.au/news/univation/sep96/deakin1.htm

Speaking of crop circles and little green men, isn’t Carl Sagan’s famous comment just a re-casting of Occam’s razor?

Sagan stated: “Extraordinary claims require extraordinary proof.”

Sagan approached it from the opposite end, so to speak, but wasn’t he saying the same thing as Occam?

I’d accept Occam as an axiom; a self-evident principle that can be accepted as correct without a formal proof.