The obvious question to ask about Ockham’s razor is: why?
On what basis are we justified to think that, as a matter of general practice,
the simplest hypothesis is the most likely one to be true?
This past week I was reading an excerpt-as-an-article in Salon. It was taken from Atheist Mind, Humanist Heart by Lex Bayer (left) and John Figdor (right). Salon packaged the excerpt as The new atheist commandments: Science, philosophy and principles to replace religion. Therein, the authors argue that “Atheism need not be reactionary — it can offer constructive rules to live by.”
“Stand back, Moses: Here’s our shot,” Bayer and Figdor say in the Salon lead.
Bumptious pompousity, if not part of stand up comedy, is reactionary; I guess they don’t get it. Or maybe they are just being flip. Anyway, it was a turn off. I thought about powering down the laptop for the night but the next sentence caught my attention:
We begin by suggesting a framework of secular belief. It begins with the simple question, How can I justify any of my beliefs?
I had to read on.
[W] e quickly realize that every belief is based on other preexisting beliefs. . . .
. . . Instead of presuming source beliefs are beliefs based on faith, let’s instead regard them as the starting assumptions for a logical proof. We can put forth a set of core assumptions and then develop a broader system of belief based on those assumptions. If the resulting system fails to create a cohesive and comprehensive system of belief, then we can start over. The initial assumptions can then be reformulated until a set is found that does lead to a consistent, meaningful “theorem of life.”
One method is . . .
to favor simplicity. This is called Ockham’s razor, after the fourteenth-century philosopher and theologian William of Ockham. The “razor” refers to any principle that helps narrow possibilities. This principle states that the answer that requires the fewest assumptions while explaining all of the facts is most likely to be correct.
But the authors caution us about this:
If we apply the razor to our search for source beliefs, it follows that a system of beliefs that requires fewer source beliefs has a greater likelihood of being valid. In other words, the fewer leaps of faith (unjustifiable source beliefs) required in order to create a system of belief, the less faith we need and the more confident we can be in the outcome.
Of course, it’s possible to misuse this concept—typically by ignoring the requirement to explain all the facts. For example, the hypothesis that height alone determines a person’s weight is a lot simpler than the notion that the complex interplay of a few dozen genes, diet, and exercise does so. But the simpler explanation fails to explain all the facts—namely, the stunning range of actual variation we see in real-life height-to-weight ratios. The five-foot-five sumo wrestler who weighs a hundred pounds more than the six-foot-nine basketball player presents an instant (and fatal) problem for the simpler answer. Thus, simpler is better so long as it explains all the facts.
Not being able to justify is not parsimonious unless you can be certain that you have all the facts. It’s not just not explaining all the facts. It’s knowing what the facts are that can be the problem.
How often do we invoke Ockham’s Razor in this blog? In just the first half of this month we have have encountered:
- Charles Freeman responding to John Green:
I still cannot see why you think the Shroud is outside the ordinary as a physical object other than that it was kept rather than being thrown away as we know most linens were after their colours had faded. Still please go on with your researches. You are certainly not into Occam Razor country!
- John Klotz reacting to Charles Freeman:
Amid all the tumult an debate, I think that applying Occam’s razor, the simplest solution, requiring the fewest assumptions is that the Shroud is what it purports to be, the burial cloth of Jesus Christ.
- Colin Berry addressing Charles Freeman:
It’s the subtlety of the TS image , both as-is, and the way it responds to modern technology that should have told you the TS was no ordinary image, certainly not painted. Flaked-off paint? The onus is on you to deal with Occam’s Razor.
- And Colin Berry addressing the lack of directionality in the images:
Is it any wonder that some see the subject itself as the source of radiant energy, wavelength usually unspecified, albeit with handy orthogonal projection and ability to ‘scorch’ linen across air gaps, provided (a) they don’t exceed 3.7cm and (b) Occams’s razor is kept in its protective sheath.
Two and a half years ago I posted the following:
Taking Ockham’s Razor to Ockham’s Razor
There is a whole lot of wisdom in a brief paper by Massimo Pigliucci over at Rationally Speaking:
. . . Philosophers often refer to this as the principle of economy, while scientists tend to call it parsimony. Skeptics invoke it every time they wish to dismiss out of hand claims of unusual phenomena (after all, to invoke the “unusual” is by definition unparsimonious, so there).
. . . The obvious question to ask about Ockham’s razor is: why? On what basis are we justified to think that, as a matter of general practice, the simplest hypothesis is the most likely one to be true? Setting aside the surprisingly difficult task of operationally defining “simpler” in the context of scientific hypotheses (it can be done, but only in certain domains, and it ain’t straightforward), there doesn’t seem to be any particular logical or metaphysical reason to believe that the universe is a simple as it could be.
What proof is there that the philosopher Franciscan friar William of Ockham (1288-1348) was right? How much science has been decided by taking leap of faith in Ockham?
Both sides in the Shroud of Turin debate invoke Ockham as a weapon of choice, it seems, in every debate.
A MUST READ: Razoring Ockham’s razor
Ockham’s razor (criterion of simplicity) is not at all the main weapon in the hands of historians and philosophers. For sure, it is the most popular, the most discussed, but not the most important.
From my article published last year in the Heythrop Journal (“The Shroud of Turin: A Historiographical Approach”):
“Historical criteria do not fall from the sky; they are part of a slowly-built-up methodology routinely used by historians, whatever may be their opinion on the subject being discussed. This article will use criteria specified by Christopher Behan McCullagh. One can list these in order of priority from the most important to the least; this list, while not written in stone, provides a general idea of the most important conditions to satisfy. Thus one has: 1) plausibility: does our knowledge in other well-known fields support or reinforce the hypothesis? 2) Explanatory scope: can the hypothesis do justice to all the facts? 3) Explanatory power: the hypothesis has to be specific and accurate, rather than ambiguous. 4) Less ad hoc: ceteris paribus, the hypothesis should not invoke or rely on unverified data (this includes the criterion of simplicity). 5) Illumination: does the hypothesis shed light on other widely accepted phenomena? This last criterion was added by Licona who believes it contributes further specification.”