Assorted laws and paradoxes

Mostly-eponymous laws I would confound without this note


I always need these laws but they are not mnemonic, y’know? The list of Hacker’s Laws is another handy reference here. Andrew Gelman’s scruffy Handy Statistical Lexicon has a lot more, especially useful for my field.

Jevons Paradox

In economics, the Jevons Paradox (/ˈdʒɛvənz/; sometimes Jevons effect) occurs when technological progress or government policy increases the efficiency with which a resource is used (reducing the amount necessary for any one use), but the rate of consumption of that resource rises due to increasing demand. The Jevons paradox is perhaps the most widely known paradox in environmental economics.

See also induced demand.

Goodhart’s law

Goodhart’s law is an adage named after economist Charles Goodhart, which has been phrased by Marilyn Strathern as “When a measure becomes a target, it ceases to be a good measure.”

Goodhart first advanced the idea in a 1975 article, which later became used popularly to criticize the United Kingdom government of Margaret Thatcher for trying to conduct monetary policy on the basis of targets for broad and narrow money. His original formulation was:

Any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes.

The verb form is fun as in don’t goodhardt yourself.

I occasionally embarrassingly confuse Goodhart’s law with the next one:

Godwin’s Law

is an Internet adage asserting that “As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1”.

Gresham’s Law

The law was

named after Sir Thomas Gresham, a sixteenth-century financial agent of the English Crown in the city of Antwerp, to explain to Queen Elizabeth I what was happening to the English shilling. Her father, Henry VIII, had replaced 40 percent of the silver in the coin with base metals, to increase the government’s income without raising taxes. Astute English merchants and even ordinary subjects would save the good shillings from pure silver and circulate the bad ones; hence, the bad money would be used whenever possible, and the good coinage would be saved and disappear from circulation.

This one is fertile for metaphor despite sounding boring. Consider it applied by critics to Bitcoin, where we might argue that illicit uses of Bitcoin will drive out licit uses. (“bitcoin is for crime”).

Moore’s Law

says wikipedia:

is the observation that the number of transistors in a dense integrated circuit doubles about every two years. The observation is named after Gordon Moore, the co-founder of Fairchild Semiconductor and CEO of Intel…

The doubling period is often misquoted as 18 months because of a prediction by Moore’s colleague, Intel executive David House. In 1975, House noted that Moore’s revised law of doubling transistor count every 2 years in turn implied that computer chip performance would roughly double every 18 months

Moore’s Law of Mad Science

Moore’s Law of Mad Science:

Every eighteen months, the minimum IQ necessary to destroy the world drops by one point.

Poe’s Law

There is no parody so extreme that someone on the internet cannot take it for earnest. Or, indeed, the other way around, there is much reality that is so extreme it must surely be parodic. (Compare Littlewood’s Law).

How do you tell if the Landover Baptist Church is real or satire? This kind of thing is a “Conservapedia problem”. Apparently the mechanism is called “Poe’s Law”.

The core idea of Poe’s Law is that a parody of something extreme can be mistaken for the real thing, and if a real thing sounds extreme enough, it can be mistaken for a parody (all because parodies are intrinsically extreme, in case you haven’t noticed it). This can also happen to someone whose picture of the opposing position is such a grotesque caricature that it renders them unable to tell parody from reality.

See also TVTropes.

Zawinski’s Law of Software Envelopment

Every program attempts to expand until it can read mail. Those programs which cannot so expand are replaced by ones which can.

Attributed to Zawinski here and refuted here.

These days a program is more likely to grow until it includes a web browser, or just cut to the chase and start as a web-browser, and grow some other features.

Hofstadter’s Law

It always takes longer than you expect, even when you take into account Hofstadter’s law.

Littlewood’s law of miracles

Found via Gwern in Littlewood’s Law of Media:

[This] illustrates a version of Littlewood’s Law of Miracles: in a world with ~8 billion people, one which is increasingly networked and mobile and wealthy at that, a one-in-billion event will happen 8 times a month.

Human extremes are not only weirder than we suppose, they are weirder than we can suppose.

Hanlon’s razor

The earliest version seems to be Goothe in 1774, but let us stick to the 1980 English language version like good anglocentrics:

Never attribute to malice that which is adequately explained by stupidity

Newton’s flaming laser sword

Mike Alder’s positivism from the trenches:

what cannot be settled by experiment is not worth debating

Tesler’s Law

Tesler’s Law, a.k.a. The Law of Conservation of Complexity states

there is a certain amount of complexity in a system which cannot be reduced.

Some complexity in a system is ‘inadvertent’. It is a consequence of poor structure, mistakes, or just bad modeling of a problem to solve. Inadvertent complexity can be reduced (or eliminated). However, some complexity is ‘intrinsic’ as a consequence of the complexity inherent in the problem being solved. This complexity can be moved, but not eliminated.

One interesting element to this law is the suggestion that even by simplifying the entire system, the intrinsic complexity is not reduced, it is moved to the user, who must behave in a more complex way.

Connection to the problem of the simplest thing.

Gall’s Law

Says wikipedia

Gall’s Law is a rule of thumb for systems design from Gall’s book Systemantics: How Systems Really Work and How They Fail. It states:

A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system.

This law is essentially an argument in favour of underspecification: it can be used to explain the success of systems like the World Wide Web and Blogosphere, which grew from simple to complex systems incrementally, and the failure of systems like CORBA, which began with complex specifications.