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Is Occam’s Razor science ? January 21, 2007

Posted by dorigo in Blogroll, physics, science.

In the comments section of a post about Charles Murray at Uncertain Principles  I found Chad stating that

Occam’s razor is not science. The scientific method does not consist of looking at the world, constructing multiple theories which might explain the observed facts, and then choosing the simplest.

Occam’s razor is meta-science at best, and not a decisive argument in any way. Sometimes, the more complicated theory is the right one.

Well, well, well, while I usually concur with Chad’s opinions, I am not sure I agree with him on this one. Occam’s razor does not consist in constructing multiple theories, but rather to advise succintness in construction of a scientific theory. It is often quoted as a lex parsimoniae:

entia non sum multiplicanda praeter necessitatem“,

that is, entities must not be multiplied beyond necessity. In this sense, I believe William of Ockham gave a real contribution to the scientific method.

Whether we should include the above law in the corpus of principia outlining the way science should be done, it is open to discussion. The scientific method is based on rational reasoning, on the systematic observation of the physical world through repeatable experiments, and on the creation of theories which agree with observed empirical facts and are liable to be disproven. Is there room for Occam’s razor ?

Sure, one cannot prefer a theory to another based uniquely on their relative parsimony. But the lex parsimoniae is indeed a strong guidance in the formulation of theories, so much so that scientists have interiorized it deep in the headquarters of their logical reasoning, no less than other fundamenta such as the time-ordering of cause and effect. They can construct exotic theories and they sometimes do, but they keep a restrained attitude even then. It is built in their genes.

Of course, I am talking about real scientists here, not about philosophers who come to like so much a theoretical construct to believe it must represent reality against all odds. They have abandoned the scientific method long ago. You know who I am talking about!

Long live Occam’s razor. These are not times when we can lighten our baggage to travel faster: these are times when we need as much rigor as we can give to ourselves in the investigation of the physical world.


1. Chad Orzel - January 21, 2007

I posted a reply comment over on my post, before I saw this here. I’d cut and paste the full text, but there’s no reason to echo all the comments back and forth…

2. Kea - January 22, 2007

Great post. I can’t help being suspicious (and I apologise for that, Chad) that Chad has been unduly influenced by String hype. One cannot create a new Theory (and Strings does not yet qualify for that title) without Occam’s razor as a beacon. Life is confusing enough.

3. Aaron Bergman - January 22, 2007

Chad and string hype?

Now that’s amusing….

4. honestpoet - January 22, 2007

Lovely post. I found your blog tagsurfing. I’ll have to check it out further at a later date & so have subscribed. Glad to coast across this!

5. dorigo - January 22, 2007

Well said, Kea. Life is indeed confusing enough that we do need that kind of guidance these days.

Aaron, I am in no position to judge – we should ask Chad. Chad, your turn to speak up🙂

6. riqie arneberg - January 22, 2007

Are cause and effect really time ordered, or is it merely our perception which is ordered by these events? This is a serious question. We all “experience” time, but the only thing any of us can experience is the feedback our senses give us.

7. dorigo - January 22, 2007

Hi Riqie,

this is indeed a quite serious question, and I am afraid I am not qualified enough to answer it meaningfully. What I can say is that while the majority of my colleagues would place time ordering of cause and effect high in their list of principia, there are indeed a few who would be less categoric about it, and some who would actually question the very existence of time. I suggest warmly Lee Smolin’s book “The trouble with Physics” for some interesting notes on this topic. I insist, you will like the book and read it cover to cover in a week.


8. Chad Orzel - January 22, 2007

String hype? I never heard of anything like that…

9. erikrau - January 23, 2007

Though I can’t begin to address the astonishing breadth of vituperation springing from Chad’s original post, I think the Ockham’s razor issue is an interesting one.

In James Burke’s overview of science and culture, The Day the Universe Changed, he begins to wax philosophical at the end, whence:

The fact that over time science has provided a more complex picture of nature is not in itself final proof that we live by the best, most accurate model so far. (337)

Which I guess is either banal or heretical, depending on your point of view.

10. dorigo - January 23, 2007

For sure Chad must be kidding – “never heard of string hype”… A nice way to cut the discussion short🙂
Anyway, in the parallel thread on his site (not for the faint-hearted, since they are also discussing IQs there) Chad remarks that

“I don’t object to Occam’s razor as a sort of useful heuristic, but it’s not decisive. You can say of two theories “Well, this one seems simpler, so I think it’s on the right track,” but that doesn’t prove anything. It might be a good way to determine which of two expensive and complicated sets of experiments would be better to undertake (the simpler theory stands a better chance of being confirmed), but experiments are the only real way to distinguish between theories.”

I agree, but I see OR as a way of reasoning, rather than a sword with which to cut knots. Yes, a useful heuristic, but a quite important one. Not a way to pick a theory between many, rather a way to construct one from scratch. In this sense, it is much more useful.

When confronted with some phenomenon with apparently no explanation within the accepted framework, one has a choice between invoking new as-of-yet unobserved entities or to dig deeper in explanation within the framework. I like Sherlock Holmes way of putting it (quoting by heart): “Once the impossible has been discarded, what is left, as improbable as it may be, is usually the correct explanation.”


11. The Say of the Week « A Quantum Diaries Survivor - January 23, 2007

[…] SoW is triggered by the discussion on Occam’s Razor… A scientific principle or metascience […]

12. Babe In The Universe - January 27, 2007

Hurray for that medieval Monk, William of Occam! His Razor outlasted Ptolemy’s epicycles and will last a lot longer than today’s epicycles.

13. From The Sidelines - Occam’s Razor and ‘Real’ Science « - February 10, 2007

[…] of whether or not Occam’s Razor is ‘real’ science or not (see, for example, this interesting discussion). I’m very much on the sidelines on this, but as an experimentalist I […]

14. Ockham's Schmockhams.... - February 27, 2007

I agree with Chad. I think people like the idea of Ockham’s Razor because they think it is so simple. Too bad that people are prone to magical thinking and forget about all the explanations that were thought to be simple but were just flat out wrong.

15. dorigo - March 9, 2007

I do not find the occam’s principle simple, schmockams. I find it useful in giving one a plan of investigation, not at selecting the right theory.


16. SUSY more unlikely by the new CDMS II results « A Quantum Diaries Survivor - March 5, 2008

[…] After this detailed and exhaustive account of supersymmetric extensions of the standard model, let me tell you what are the news from CDMS II, a detector designed to detect weak interacting massive particles. WIMPs, as they are called, could be the cause of observed disagreement between the amount of luminous mass in the universe and the motion we observe: Dark Matter. It is to be noted that strictly speaking WIMPs do not only belong to SUSY, although a SUSY WIMP would nicely kill two big birds with one small stone – a nice feature for an Ockhamist. […]

17. Alf - March 6, 2008

Probably one can think of Occam’s Rasor as a higher level “Minimal Action Principle”.

However, imagine what physics would look like if William of Ockham were not a Franciscan but a follower of John XXII instead…

18. dorigo - March 6, 2008

Sure, the razor of Ockham is a kind of meta-MAP. But your comment on John XXII is obscure to me, can you clarify ?


19. Alf - March 7, 2008

William of Ockham was a Franciscan, so his ‘minimalism’ is a part of
the bigger picture of poverty being the right way to follow God.
This was exactly the opposite of the official Vatican politics
(which we can probably describe as “the more,the better”).

Science chose to take one of the sides in this dispute which is both
metaphysical and practical.
Still, it seems that the question is still here.
Sorry to profanise the discussion.

20. dorigo - March 7, 2008

Hi Alf,

thank you for the explanation. I agree, the principle is quite franciscan in philosophy. Of course you need not apologize, the discussion here was basically dead since a year ago… And in any case your contribution is welcome.


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