All Ideas Having Large Consequences Are Always Simple

When Thomas Huxley finished reading On the Origin of Species in 1859, he is reported to have said how extremely stupid it was not to have thought of that. The remark has lasted because it captures what many readers feel about the book. Its central idea can be stated in a sentence, that creatures vary, that the variations are inherited, and that those best fitted to their surroundings leave more offspring. A schoolchild can grasp it, and yet it has reorganised biology, medicine and our understanding of ourselves. The topic claims that this is the rule, and that ideas of large consequence are always simple.

There is more evidence. The shipping container, introduced by the trucking entrepreneur Malcom McLean in April 1956 when his converted tanker carried fifty eight metal boxes from Newark to Houston, involved nothing more than putting goods into a standard box that could be moved between ship, train and truck without being unpacked. The cost of shipping fell so far that a global network of factories became possible, and the modern economy of Asian manufacturing was built on it. An idea that a child might have had remade world trade.

Mathematics supplies its own examples. The Indian use of zero as a number in its own right, which Brahmagupta set out in 628 CE with rules for adding and subtracting it, is among the simplest conceptions imaginable. It made written arithmetic so much easier that merchants and astronomers across Asia and Europe adopted the system that carried it. Double entry bookkeeping, set out by Luca Pacioli in 1494, is just the rule that every transaction is recorded twice, as a gain in one account and a loss in another, and it made large scale commerce and later corporations manageable.

Politics and ethics have simple ideas too. Gandhi's satyagraha rested on the plain conviction that a person can resist injustice without hurting his opponent and can, by suffering willingly, appeal to the opponent's conscience. In 1930 a march to the sea to make a pinch of salt in defiance of a tax challenged the authority of an empire. Everyone understood it at once, and that was its power. The ideas of the equality of persons and of consent of the governed, however hard to realise, are also few in words and immense in their effects.

Everyone understood it at once, and that was its power.

Computing offers another case. In 1936 Alan Turing described an imaginary machine that reads and writes symbols on a tape according to a short table of rules, and showed that such a machine can carry out any calculation that can be specified. Every computer since descends from that toy, and the phone in a student's hand is more complicated in its engineering than anyone in 1936 could have imagined, though the principle fits on a page.

Why should this be so? One reason is that ideas must travel. A concept that cannot be passed from mind to mind cannot spread, and those that spread are those that can be remembered and repeated. A complicated theory needs specialists to carry it, and its consequences wait on their numbers. A simple one can be taken up by the farmer, the trader and the soldier alike, and so it multiplies. Large consequences require many people to act on an idea, and many people can act only on what they can grasp.

A second reason is more philosophical, and it concerns what thinkers find satisfying. The scientist and the thinker value economy of explanation. Ockham's razor, from the fourteenth century, advises that explanations should not multiply entities beyond necessity, and physicists have often found that the right theory is the one that is elegant. Newton's law of gravitation applied to a falling apple and to the moon with the same equation. A deep idea tends to unify many facts under one principle, and the unification is what feels simple to the person who finally sees it.

But the claim needs several qualifications. First, simplicity is partly an illusion of hindsight. After Darwin or Newton has spoken, the idea seems obvious, but before that it was hidden behind the confusions of the age. Huxley's regret was possible only because Darwin had spent twenty years collecting evidence, and the sentence that seems simple compresses a mountain of observation. The steps required to see simplicity were not simple. What looks effortless was reached by effort, and hindsight conceals it.

Second, some of the most consequential ideas are not simple at all. Einstein's general relativity requires a mathematics that took him a decade to master, and quantum mechanics offends common sense and yields to few analogies. The theory of evolution may be stated in a sentence, but understanding how it works in genetics, development and ecology occupies whole careers. Only the slogan is simple, and the consequences depended on the work behind it. Simplicity of statement should not be confused with simplicity of content.

Third, simple ideas can be simply wrong, and still have large consequences. The belief that the races of mankind are ranked by nature was an easy idea, and it justified slavery, colonial conquest and genocide. Lysenko's claim in the Soviet Union that acquired traits could be inherited was simple and politically attractive, and it set Soviet biology back by decades and may have contributed to famine. The attraction of simplicity is also its danger, since a simple falsehood travels as fast as a simple truth. Many large catastrophes were driven by ideas that were easy to believe.

This leaves a puzzle in the topic's word always. Any single exception defeats it, and we have found several. The claim seems better understood as a pattern about how ideas gain influence, which may hold for most cases, than as a law. Yet even as a tendency it may be an illusion of selection, because we remember the simple ideas that succeeded and forget the many complicated ones that quietly shaped the world without ever being summarised. The ideas of greatest consequence may be those we have never learnt to state in a sentence.