Berlin, 1929. The poet and journalist George Sylvester Viereck has charmed an interview out of an initially reluctant superstar physicist?. He asks: "How do you account for your discoveries? Through intuition or inspiration?" Albert Einstein replies:

"Both. I sometimes feel I am right, but do not know it. When two expeditions of scientists went to test my theory I was convinced they would confirm my theory. I wasn't surprised when the results confirmed my intuition, but I would have been surprised had I been wrong. I'm enough of an artist to draw freely on my imagination, which I think is more important than knowledge. Knowledge is limited. Imagination encircles the world."

Knowledge versus imagination. Einstein's aphorism  reflects a recurrent theme in human thought. The ancient dichotomy between what we know and what we dream, intuit or sense by instinct is found, in some form, in every field of human intellectual endeavour. It is seen in the contrast between rationalist and mystic interpretations of the world's great religions, between realism and surrealism in the visual arts and between the brutal number-crunching of much experimental physics and the feathery abstractions of superstring and membrane theory.

Artists, geniuses and other rebellious spirits have often claimed imagination as their territory. Knowledge, that dull conviction resulting from a brush with reality, is black-and-white, logical, stable, conservative ¨C the domain of curators and  accountants. Your view of which is more important will depend on your personality. The relevant distinction was best captured not by a psychology text but by a history book (of sorts): in their discussion of the English Civil War, Sellars and Yeatman famously described the Cavaliers as "wrong but wromantic" and the Roundheads as "right and repulsive". Who'd be a Roundhead? Who won the Civil War?

ÖйúAƬ

Like many dichotomies, this one is an oversimplification. We know that the brilliance of many great artists was grounded in years of hard training; we know some excitingly imaginative museums and some highly creative accountants. Throughout our development as a species we have relied on a blend of imagination and knowledge. Both are valuable. What then is the relationship between them?

Metaphors are plentiful. Knowledge is a stepping stone to imagination; it stands to imagination as honeycomb does to honey; knowledge and imagination are enemies, or independent strands in the web of our mental lives. The Oxford English Dictionary states that imagination involves "forming a mental concept of what is not actually present to the senses". But the full flavour of Einstein's aphorism eludes this definition. I can form a mental concept of what I ate at last week's dinner party, though it is no longer present to any of my senses (even those rarely-discussed but useful ones which signal the state of my bowels). Imagination is something more than memory, something novel: adding a movie star or picturing the guests without their clothes.

ÖйúAƬ

Knowledge concerns itself with what is present to the senses, but is also a stored and shared repository of publicly acceptable thoughts, many frozen into physical symbols (written or spoken), transmitted through time and space. Knowledge coded, stored and expressed using symbols can, because of the entrancing flexibility of symbol systems, be broken up and reassembled in a multitude of novel combinations. It is this act of recombination which underlies the power to imagine. Our imagination is and must be grounded in our knowledge. The more memories we accumulate, the more material we have to work with, the richer and stranger are the fruits of our imagination.

Imagination, however, is not just the recombination of stored experiences. Such recombination happens every night even in organisms blessed with much less cortex than human beings. What distinguishes us is our capacity for controlled and wakeful dreaming. This is a useful survival aid, helping us to solve problems, anticipate challenges and conceive alternatives. But we have turned imagination into much more ¨C a good in itself. Like money, sex or drugs, we use it to satisfy our needs, flaunt our wealth and status, tighten our social bonds, or distract us from realities we would rather avoid.

The comparison with drugs implies the risk of addiction, and indeed, our urge to imagine, and to consume the products of other people's imagination, can sometimes become extreme. Reality can be a bleak place, especially for those who lack the essential antidote: love. When depression sets in, an individual may lose the strength to use imagination to counteract the automatic, overwhelmingly negative thoughts characteristic of the condition. The products of others' imaginations provide an alternative.

A best-selling page-turner or fast-paced movie thriller draws us into another world. These fake worlds, from the fantasy of Harry Potter to the horror of Hannibal Lecter, have two ingredients in common which make them attractive to millions. Firstly, they provide an opportunity for "losing" oneself in an absorption where consciousness of self-as-independent-entity disappears: a sweet, safe, temporary death. Secondly, they deny Darwin, confirming Eliot's view that "humankind cannot bear too much reality". In a fake world the hero or heroine is special and recognised as such by others. An uncaring universe cannot destroy them, indeed, they are at its centre; if they die the fake world dies with them. Voldemort focuses on attacking Harry Potter, Lecter on tantalising yet protecting his adversary Clarice Starling. Identifying with a person who interests such potent beings does no harm to the self-esteem. In some individuals such cognitive massage can become an obsession in a world where the public ideal is super-confidence.

Here again we see the complementarity of imagination and knowledge. At both group and individual levels, knowledge facilitates community and continuity, while imagination facilitates change. Knowledge binds us to a sometimes-oppressive existence; imagination helps us escape it. However, imagination evolved as a tool for facilitating survival. Imagining, we take a step beyond what we know into the future or into another world. We see alternatives and possibilities; we work out what we need to reach our goals. Unhooked from reality, imagination no longer serves these life-enhancing purposes. Without new knowledge to feed it and keep it in check, it can become sterile and even dangerous: in Hume's words, "nothing but sophistry and illusion".

Another measurable way of thinking about the balance between imagination and knowledge (the "I/K ratio") is to consider each as private or public, individual or group. Wittgenstein famously argued that language is essentially public, requiring consensus about the use of its symbols in order to maintain consistency in meaning over time. One might say the same about knowledge: it must derive from experience in a way which can in principle be reproduced by others. Imagination is a private thing, the leap of a single brain from established fact to exciting novelty.

ÖйúAƬ

Again the dichotomy is too simplistic. Knowledge strengthens group bonding, but the emergence of new knowledge in, for example, the sciences can threaten a group's very existence. Imagination can challenge rules and traditions by putting information together in novel ways; yet shared acts of imagination can also help to strengthen intra-group bonds. Try daydreaming: generate for yourself a coherent story of your own invention, follow it through from beginning to end. Unless you are a professional storyteller you will probably find it extremely difficult to avoid drifting into other thoughts or even falling asleep. We think of ourselves as the only species capable of controlled dreaming, but in fact it is hard to keep control unless we make our dreams public. The greatest acts of imagination ¨C from Bach's Cello Suites or Milan Cathedral to Star Wars or G¨¹nther van Hagen's Bodyworlds ¨C require not only creation but admiration: they depend for their impact on being heard, seen and understood within a cultural context built up over hundreds of years by thousands of people.

Was Einstein right? Is imagination more important than knowledge? As our realities become more complex we seem increasingly to prefer imagination, but that preference is culture-dependent. Imagination flourishes when its products are highly valued. Leisure, wealth and a degree of political stability are prerequisites for the freedom essential to creativity and for the use of artistic products as indicators of social status.

ÖйúAƬ

When a society feels under threat, shared knowledge, exalted as "culture" or "tradition", may be valued more, lowering the I/K ratio. Resources previously dedicated to artistic creativity may be diverted into attempts to protect the society or to acquire knowledge about the changes it is experiencing, leading to reduced artistic output. Art in Renaissance Florence provides an example. Between the Milanese siege of 1401-2 and the French invasion in 1494 a period of relative political stability was the context for some of the greatest paintings and sculptures of the Renaissance. In the chaos of the early 16th century, as power fluctuated between Medici and republican governments, comparatively little great art was produced. Political theory, however, blossomed, notably with the publication of Machiavelli's The Prince and Discourses .

That the I/K ratio is culture-dependent is surely unsurprising. Even within a single society, the preferred I/K ratio in any given field of intellectual activity will depend on the field in question and on the person making the assessment.

This brings us to another aspect of the complementarity between knowledge and imagination: its dynamic nature. The I/K ratio changes over time. In some cases, a new branch of the sciences, for example, can begin with a few mavericks (high I/K ratio) whose research is initially dismissed as speculative. As their way of thinking gradually wins acceptance, it attracts recruits at an increasing rate until a paradigm shift occurs and allegiances transfer wholesale from the old establishment to the new. A period of growing stability follows in which knowledge is assembled (decreasing I/K ratio) which supports the new ideas. Creative output falls, stagnation gradually sets in. Problems begin to emerge, which are ignored by all but a few ... and so the cycle begins again.

As for science, so for religion. Cults often start with an act of radical imagining, what Anthony Wallace calls a "mazeway resynthesis": elements of current cultural understanding (the "mazeway") are recombined into a new and dramatic form which seems to promise solutions to previously insoluble problems. Yet cult doctrines, born in the fiery freedom of imagination, tend to solidify into the restriction of dogma, leading to the rejection of any information which does not fit. As social psychologists have noted, however, the pattern of growth, stability and attrition seems to be a fundamental one for human groups across many different fields of endeavour.

So is imagination more important than knowledge? It depends on whom you ask, what you ask about, and when.

Kathleen Taylor is a research scientist in the department of physiology at Oxford University. This essay won the THES /Palgrave Humanities and Social Sciences Writing Prize.

ÖйúAƬ

________

? The interview was published in the Philadelphia Saturday Evening Post , October 26th, 1929.