As the home computer spread across the globe, and became inextricably wired into the Internet's extelligence, an environment was created that gave birth to an insidious silicon-based form of meme: the computer virus. All viruses so far seem to have been written deliberately by humans, although at least one turned out to be a far more successful replicator than its designer had intended, thanks to a programming error. 'Artificial life' simulations using evolving computer programs are often run inside a 'shell' that isolates them from the outside world, because of the unlikely but possible evolution of a really nasty computer virus. The world's computer network is certainly complex enough to evolve its own viruses, given enough time.

Memes are mind-viruses.

In The Meme Machine, Susan Blackmore says that 'Memes spread themselves around indiscriminately without regard to whether they are useful, neutral, or positively harmful to us.'

The song 'Happy Birthday to You' is mostly harmless, although it is just about possible to see it as an insidious piece of propaganda for global commerce if you're that way inclined. Advertising is a conscious attempt to unleash memes; a successful advertising campaign starts to build its own momentum as it spreads by word of mouth as well as overt TV or newspaper ads. Some advertising is beneficial (Oxfam, say) and some is manifestly harmful (tobacco). In fact, many memes are harmful, but still propagate very effectively: among them are the chain-letter and its financial analogue, pyramid selling. Just as DNA propagates without having any conscious intentions of its own, so memes replicate without having conscious objectives. The people who set the memes loose may have had overt intentions, but the memes themselves don't. Those that perform well, leading human minds to pass them on in quantity, thrive; those that do not, die out, or at best live on as small, isolated pockets of infection. The spread of a meme is much like the spread of a disease. And just as you can protect yourself against some diseases, by taking the right precautions, you can also protect yourself against becoming infected with a meme. The ability to think critically, and to question statements that rest on authority instead of evidence, are quite effective defences.

This is our message to you. You need not be a victim of the power of story, like Vorbis the Quisitor, smitten by an earthbound tortoise, the Wrath of Om. You can be a Granny Weatherwax, sailing through story-space like a master navigator, attuned to every breath of narrative wind (and a lot of it is, mark you), tacking against the gale like a maverick, avoiding the Shoals of Dogma and the Scylla and Charybdis of Indecision ...

Sorry, we got carried away. What we mean is: if you understand the power of story, and learn to detect abuses of it, you might actually deserve the appellation Homo sapiens.

Blackmore's book argues that many aspects of human nature are explained much better by memetics, the mechanisms whereby memes exist and propagate, than by any existing rival theory. In our terminology, memetics illuminates the complicity between intelligence and extelligence, between the individual mind and the culture of which it is but one tiny part. Some critics counter that the memeticists can't even say what the basic unit of a meme is. For example, are the first four notes of Beethoven's Fifth Symphony (dah-dah-da DUM) a meme, or is the meme really the whole symphony? Both replicate successfully: the second in the minds of music-lovers, the first in a weird variety of minds.

However, this kind of criticism never carries much weight when a new theory is being developed. Not that this stops the critics, of course. By the time a scientific theory can 'define' its concepts with complete precision, it's dead. Very few concepts can actually be defined completely: not even something like 'alive'. What, precisely, does 'tall' mean? 'Rich'? 'Wet'?

'Convincing'? Let alone 'slood'. If it comes to the crunch, the basic unit of genetics has not been defined in any convincing way, either. Is it a DNA base? A DNA sequence that codes for proteins, a 'gene' in the most limited sense? A DNA sequence with a known function -a 'gene' in its broadest sense? A chromosome? An entire genome? Does it have to exist inside an organism?

Most DNA in the world contributes nothing genetic to the future: there's DNA in dead skin flakes, falling leaves, rotting logs ...

Dawkins's famous phrase 'It is raining DNA outside', applied to downy seeds of the willow tree at the start of chapter 5 of The Blind Watchmaker, is poetic. But very little of that DNA leads anywhere; it's just another molecule to be broken down as the falling seeds rot. A few seeds survive to germinate; fewer still produce plants; and most of those die or are eaten before they grow into a willow tree and produce the next rainfall of seeds. DNA has to be in the right place

(in sexual species, eggs or sperm) at the right time (fertilisation) before it propagates itself in any genetic sense. None of this stops genetics being a real science, and a very exciting and important one. So the fuzziness of definitions is not a good stick with which to beat the memetic dog, or indeed any dog that has anything going for it.

In his original discussion, almost as an aside, Dawkins suggested that religion is a meme, which goes something like 'If you wish to avoid the everlasting fires, you must believe this, and pass it on to your children'.76 The popularity of religion is no doubt more complicated than that; nevertheless, there is the germ of an idea here, because that sentence does correspond rather closely to the central message of many -not all -religions. The theologian John Bowker was sufficiently disturbed by this suggestion that he wrote Is God a Virus? to shoot it down. The fact that he bothered shows that he saw it as an important (and from his viewpoint dangerous)

question.

Blackmore recognises that a religion, or any ideology, is too complex to be propagated by a single meme, just as an organism is too complex to be propagated by a single gene. Dawkins recognised this, too, and came up with a concept that he called 'coadapted meme complexes'.

These are systems of memes that replicate collectively. The meme 'If you wish to avoid the everlasting fires, you must believe this, and pass it on to your children' is too simple to get very far, but if it is allied to other memes like 'The way to avoid the everlasting fires can be found in the Holy Book' and 'You must read the Holy Book or face eternal damnation', then the whole collection of memes forms a network that replicates far more effectively.

A complexity theorist would call such a collection of memes an 'autocatalytic set': each meme is catalysed, its replication is assisted, by some or all of the others. In 1995 Hans-Cees Speel coined the term 'memeplex'. Blackmore has a whole chapter on 'Religions as memeplexes'. If this line of argument bothers you, hang on a minute. Are you saying that religion is not a collection of beliefs and instructions that can be passed very successfully from one person to another? That's what 'memeplex' means. Anyway, replace 'religion' by 'political party' if you want to -not the one you support, naturally. Those other idiots who advocate/despise (delete whichever is inapplicable) free market economics, state pensions, public ownership of industry, private ownership of public services ... And bear in mind that while the secret of the spread of your own religion may be that it is The Truth, that can't possibly be the secret of the spread of all those other false religions in the world. Why the devil do sensible people believe that kind of rubbish?

Because it is a successful memeplex.

The evidence for memetic transmission of ideologies is extensive. For example, every one of the world's religions (barring ancient ones whose origins are lost in the mists of time) seems to have started with a very small group of believers and a charismatic leader. They are specific to particular cultural backgrounds; the meme needs a fertile substrate on which to grow. Many cherished beliefs of Christianity, for example, seem absurd to anyone not brought up in the Christian tradition. Virgin birth? (Well, that one was actually an inspired mistranslation of the Hebrew for 'young woman', but no matter.) Restored the dead to life? Communion wine becomes blood? Communion wafers are the body of Christ -and you eat them? Really? To believers, of course, all this makes perfect sense, but to outsiders, uninfected by the meme, it's laughable.77