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My clerical correspondent of the previous chapter found faith through a wasp. Charles Darwin lost his with the help of another: “I cannot persuade myself,” Darwin wrote, “that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars.” Actually Darwin 's gradual loss of faith, which he downplayed for fear of upsetting his devout wife Emma, had more complex causes. His reference to the Ichneumonidae was aphoristic. The macabre habits to which he referred are shared by their cousins the digger wasps, whom we met in the previous chapter. A female digger wasp not only lays her egg in a caterpillar (or grasshopper or bee) so that her larva can feed on it but, according to Fabre and others, she carefully guides her sting into each ganglion of the prey's central nervous system, so as to paralyze it but not kill it. This way, the meat keeps fresh. It is not known whether the paralysis acts as a general anesthetic, or if it is like curare in just freezing the victim's ability to move. If the latter, the prey might be aware of being eaten alive from inside but unable to move a muscle to do anything about it. This sounds savagely cruel but as we shall see, {96} nature is not cruel, only pitilessly indifferent. This is one of the hardest lessons for humans to learn. We cannot admit that things might be neither good nor evil, neither cruel nor kind, but simply callous – indifferent to all suffering, lacking all purpose.

We humans have purpose on the brain. We find it hard to look at anything without wondering what it is “for,” what the motive for it is, or the purpose behind it. When the obsession with purpose becomes pathological it is called paranoia – reading malevolent purpose into what is actually random bad luck. But this is just an exaggerated form of a nearly universal delusion. Show us almost any object or process, and it is hard for us to resist the “Why” question – the “What is it for?” question.

The desire to see purpose everywhere is a natural one in an animal that lives surrounded by machines, works of art, tools and other designed artifacts; an animal, moreover, whose waking thoughts are dominated by its own personal goals. A car, a tin opener, a screwdriver and a pitchfork all legitimately warrant the “What is it for?” question. Our pagan forebears would have asked the same question about thunder, eclipses, rocks and streams. Today we pride ourselves on having shaken off such primitive animism. If a rock in a stream happens to serve as a convenient stepping-stone, we regard its usefulness as an accidental bonus, not a true purpose. But the old temptation comes back with a vengeance when tragedy strikes – indeed, the very word “strikes” is an animistic echo: “Why, oh why, did the cancer/earthquake/hurricane have to strike my child?” And the same temptation is often positively relished when the topic is the origin of all things or the fundamental laws of {97} physics, culminating in the vacuous existential question “Why is there something rather than nothing?”

I have lost count of the number of times a member of the audience has stood up after a public lecture I have given and said something like the following: “You scientists are very good at answering ‘How’ questions. But you must admit you're powerless when it comes to ‘Why’ questions.” Prince Philip, Duke of Edinburgh, made this very point when he was in an audience at Windsor addressed by my colleague Dr. Peter Atkins. Behind the question there is always an unspoken but never justified implication that since science is unable to answer “Why” questions, there must be some other discipline that is qualified to answer them. This implication is, of course, quite illogical.

I'm afraid that Dr. Atkins gave the Royal Why fairly short shrift. The mere fact that it is possible to frame a question does not make it legitimate or sensible to do so. There are many things about which you can ask, “What is its temperature?” or “What color is it?” but you may not ask the temperature question or the color question of, say, jealousy or prayer. Similarly, you are right to ask the “Why” question of a bicycle's mudguards or the Kariba Dam, but at the very least you have no right to assume that the “Why” question deserves an answer when posed about a boulder, a misfortune, Mt. Everest or the universe. Questions can be simply inappropriate, however heartfelt their framing.

Somewhere between windscreen wipers and tin openers on the one hand and rocks and the universe on the other lie living creatures. Living bodies and their organs are objects that, unlike rocks, seem to have purpose written all over them. Notoriously, of course, the apparent purposefulness of {98} living bodies has dominated the classic Argument from Design, invoked by theologians from Aquinas to William Paley to modern “scientific” creationists.

The true process that has endowed wings and eyes, beaks, nesting instincts and everything else about life with the strong illusion of purposeful design is now well understood. It is Darwinian natural selection. Our understanding of this has come astonishingly recently, in the last century and a half. Before Darwin, even educated people who had abandoned “Why” questions for rocks, streams and eclipses still implicitly accepted the legitimacy of the “Why” question where living creatures were concerned. Now only the scientifically illiterate do. But “only” conceals the unpalatable truth that we are still talking about an absolute majority.

Actually, Darwinians do frame a kind of “Why” question about living things, but they do so in a special, metaphorical sense. Why do birds sing, and what are wings for? Such questions would be accepted as a shorthand by modern Darwinians and would be given sensible answers in terms of the natural selection of bird ancestors. The illusion of purpose is so powerful that biologists themselves use the assumption of good design as a working tool. As we saw in the previous chapter, long before his epoch-making work on the bee dance Karl von Frisch discovered, in the teeth of strong orthodox opinion to the contrary, that some insects have true color vision. His clinching experiments were stimulated by the simple observation that bee-pollinated flowers go to great trouble to manufacture colored pigments. Why would they do this if bees were color-blind? The metaphor of purpose – more precisely, the assumption that Darwinian selection is involved – is here being used to make a strong inference about the world. It {99} would have been quite wrong for von Frisch to have said, “Flowers are colored, therefore bees must have color vision.” But it was right for him to say, as he did, “Flowers are colored, therefore it is at least worth my while working hard at some new experiments to test the hypothesis that they have color vision.” What he found when he looked into the matter in detail was that bees have good color vision but the spectrum they see is shifted relative to ours. They can't see red light (they might give the name “infra yellow” to what we call red). But they can see into the range of shorter wavelengths we call ultraviolet, and they see ultraviolet as a distinct color, sometimes called “bee purple.”

When he realized that bees see in the ultraviolet part of the spectrum, von Frisch again did some reasoning using the metaphor of purpose. What, he asked himself, do bees use their ultraviolet sense for? His thoughts returned full circle – to flowers. Although we can't see ultraviolet light, we can make photographic film that is sensitive to it, and we can make filters that are transparent to ultraviolet light but cut out “visible” light. Acting on his hunch, von Frisch took some ultraviolet photographs of flowers. To his delight, he saw patterns of spots and stripes that no human eye had ever seen before. Flowers that to us look white or yellow are in fact decorated with ultraviolet patterns, which often serve as runway markers to guide the bees to the nectaries. The assumption of apparent purpose had paid off once again: flowers, if they were well designed, would exploit the fact that bees can see ultraviolet wavelengths.