From the Vault: Some Razors

On the basis that a re-post is better than no post, here is one from the vault (time having been precious for the last few days because of my involvement, in a professional capacity, in a large court case which starts on Monday . . .

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In philosophy, a razor is a principle or rule of thumb that allows one to eliminate ("shave off") unlikely explanations for a phenomenon, or avoid unnecessary actions. Or, they are guides to explaining things. 

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Occam’s Razor: 

“Entities should not be multiplied beyond necessity.” 

Simpler version: 

Simpler explanations are more likely to be correct; avoid unnecessary or improbable assumptions. 

Comments: 

• The simpler explanation must satisfy all available evidence. Just because an explanation is the simplest one available, doesn’t make it the best one. If it fails to explain or ignores key facts, then it remains problematic. The best explanation then, is the one that fits the evidence, using the fewest assumptions. 

• Occam’s Razor, named after William of Ockham (1285–1347), is also illustrated by a maxim taught to medical students: Think horses, not zebras. In other words, if investigating illness, explore the commonplace before the exotic. 

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Grice's Razor: 

As a principle of parsimony, conversational implications are to be preferred over semantic context for linguistic explanations. 

Simpler version: 

When in a conversation, prefer what the speaker meant over what the sentence he/she spoke literally meant. 

Comments: 

• Named after British philosopher and language expert Paul Grice (1913 – 1988), the razor requires that context should be looked at to determine meaning, not just what is being said, in isolation. 

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Hanlon's Razor: 

Never attribute to malice that which can be adequately explained by stupidity. 

Simpler version: 

Think stupidity before evil intent. 

Comments: 

• Named after Robert J Hanlon bit there is doubt as to whether he did in fact coin it. 

• Never rule out the possibility of stupidity and malice in combination. 

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Hitchens's Razor: 

"What can be asserted without evidence can be dismissed without evidence." 

Simpler version: 

The burden of proof regarding the truthfulness of a claim lies with the one who makes the claim, and if this burden is not met, the claim is unfounded, and its opponents need not argue further in order to dismiss it. 

Comments: 

• The concept is named, echoing Occam's razor, for the journalist and writer Christopher Hitchens, who in a 2003 Slate article formulated it thus: "What can be asserted without evidence can be dismissed without evidence". 

• The dictum also appears in God Is Not Great: How Religion Poisons Everything, a book by Hitchens published in 2007. 

• Hitchens's razor is actually an English translation of the Latin proverb quod grātīs asseritur, grātīs negātur ("What is freely asserted is freely dismissed"), which was commonly used in the 19th century. It takes a stronger stance than the Sagan standard ("Extraordinary claims require extraordinary evidence"), instead applying to even non-extraordinary claims. 

• It reminds me of the dictum expounded by James Randi and his Skeptics Foundation: If two explanations are possible for something and one is consistent with known laws of the universe and the other requires suspension of such knowledge and beliefs, the former should prevail until the second is proven. 

• Thus if a child wakes on Christmas morning and finds presents under the tree, two explanations are possible: Mum and Dad put them there the night before or Santa came down the chimney and delivered them. The former should be adopted until the second is proven.

More razors to come.