If I dream of being reunited with a dead parent or child, who is to tell me that it didn’t really happen? If 1 have a vision of myself floating in space looking down on the Earth, maybe I was really there; who are some scientists, who didn’t even share the experience, to tell me that it’s all in my head? If my religion teaches that it is the inalterable and inerrant word of God that the Universe is a few thousand years old, then scientists are being offensive and impious, as well as mistaken, when they claim it’s a few billion.
Irritatingly, science claims to set limits on what we can do, even in principle. Who says we can’t travel faster than light? They used to say that about sound, didn’t they? Who’s going to stop us, if we have really powerful instruments, from measuring the position and the momentum of an electron simultaneously? Why can’t we, if we’re very clever, build a perpetual motion machine ‘of the first kind’ (one that generates more energy than is supplied to it), or a perpetual motion machine ‘of the second kind’ (one that never runs down)? Who dares to set limits on human ingenuity?
In fact, Nature does. In fact, a fairly comprehensive and very brief statement of the laws of Nature, of how the Universe works, is contained in just such a list of prohibited acts. Tellingly, pseudoscience and superstition tend to recognize no constraints in Nature. Instead, ‘all things are possible’. They promise a limitless production budget, however often their adherents have been disappointed and betrayed.
A related complaint is that science is too simple-minded, too ‘reductionist’; it naively imagines that in the final accounting there will be only a few laws of Nature – perhaps even rather simple ones – that explain everything, that the exquisite subtlety of the world, all the snow crystals, spiderweb latticework, spiral galaxies, and flashes of human insight can ultimately be ‘reduced’ to such laws. Reductionism seems to pay insufficient respect to the complexity of the Universe. It appears to some as a curious hybrid of arrogance and intellectual laziness.
To Isaac Newton – who in the minds of critics of science personifies ‘single vision’ – it looked like a clockwork Universe. Literally. The regular, predictable orbital motions of the planets around the Sun, or the Moon around the Earth, were described to high precision by essentially the same differential equation that predicts the swing of a pendulum or the oscillation of a spring. We have a tendency today to think we occupy some exalted vantage point, and to pity the poor Newtonians for having so limited a world view. But within certain reasonable limitations, the same harmonic equations that describe clockwork really do describe the motions of astronomical objects throughout the Universe. This is a profound, not a trivial parallelism.
Of course, there are no gears in the solar system, and the component parts of the gravitational clockwork do not touch. Planets generally have more complicated motions than pendulums and springs. Also, the clockwork model breaks down in certain circumstances: over very long periods of time, the gravitational tugs of distant worlds – tugs that might seem wholly insignificant over a few orbits – can build up, and some little world can go unexpectedly careening out of its accustomed course. However, something like chaotic motion is also known in pendulum clocks; if we displace the bob too far from the perpendicular, a wild and ugly motion ensues. But the solar system keeps better time than any mechanical clock, and the whole idea of keeping time comes from the observed motion of the Sun and stars.
The astonishing fact is that similar mathematics applies so well to planets and to clocks. It needn’t have been this way. We didn’t impose it on the Universe. That’s the way the Universe is. If this is reductionism, so be it.
Until the middle twentieth century, there had been a strong belief – among theologians, philosophers and many biologists -that life was not ‘reducible’ to the laws of physics and chemistry, that there was a ‘vital force’, an ‘entelechy’, a tao, a mana that made living things go. It ‘animated’ life. It was impossible to see how mere atoms and molecules could account for the intricacy and elegance, the fitting of form to function, of a living thing. The world’s religions were invoked: God or the gods breathed life, soul-stuff, into inanimate matter. The eighteenth-century chemist Joseph Priestley tried to find the ‘vital force’. He weighed a mouse just before and just after it died. It weighed the same. All such attempts have failed. If there is soul-stuff, evidently it weighs nothing, that is, it is not made of matter.
Nevertheless, even biological materialists entertained reservations; perhaps, if not plant, animal, fungal and microbial souls, some still undiscovered principle of science was needed to understand life. For example, the British physiologist J.S. Haldane (father of J.B.S. Haldane) asked in 1932:
What intelligible account can the mechanistic theory of life give of the … recovery from disease and injuries? Simply none at all, except that these phenomena are so complex and strange that as yet we cannot understand them. It is exactly the same with the closely related phenomena of reproduction. We cannot by any stretch of the imagination conceive a delicate and complex mechanism which is capable, like a living organism, of reproducing itself indefinitely often.
But only a few decades later and our knowledge of immunology and molecular biology have enormously clarified these once impenetrable mysteries.
I remember very well when the molecular structure of DNA and the nature of the genetic code were first elucidated in the 1950s and 1960s, how biologists who studied whole organisms accused the new proponents of molecular biology of reductionism. (They’ll never understand even a worm with their DNA.’) Of course reducing everything to a ‘vital force’ is no less reductionism. But it is now clear that all life on Earth, every single living thing, has its genetic information encoded in its nucleic acids and employs fundamentally the same codebook to implement the hereditary instructions. We have learned how to read the code. The same few dozen organic molecules are used over and over again in biology for the widest variety of functions. Genes bearing significant responsibility for cystic fibrosis and breast cancer have been identified. The 1.8 million rungs of the DNA ladder of the bacterium Haemophilis influenzas, comprising its 1,743 genes, have been sequenced. The specific function of most of these genes is beautifully detailed – from the manufacture and folding of hundreds of complex molecules, to protection against heat and antibiotics, to increasing the mutation rate, to making identical copies of the bacterium. Much of the genomes of many other organisms (including the roundworm Caenorhabditis elegans) have now been mapped. Molecular biologists are busily recording the sequence of the three billion nucleotides that specify how to make a human being. In another decade or two, they’ll be done. (Whether the benefits will ultimately exceed the risks seems by no means certain.)
The continuity between atomic physics, molecular chemistry, and that holy of holies, the nature of reproduction and heredity, has now been established. No new principle of science need be invoked. It looks as if there are a small number of simple facts that can be used to understand the enormous intricacy and variety of living things. (Molecular genetics also teaches that each organism has its own particularity.)
Reductionism is even better established in physics and chemistry. I will later describe the unexpected coalescence of our understanding of electricity, magnetism, light and relativity into a single framework. We’ve known for centuries that a handful of comparatively simple laws not only explains but quantitatively and accurately predicts a breathtaking variety of phenomena, not just on Earth but through the entire Universe.
We hear – for example from the theologian Langdon Gilkey in his Nature, Reality and the Sacred – that the notion of the laws of Nature being everywhere the same is simply a preconception imposed on the Universe by fallible scientists and their social milieu. He longs for other kinds of ‘knowledge’, as valid in their contexts as science is in its. But the order of the Universe is not an assumption; it’s an observed fact. We detect the light from distant quasars only because the laws of electromagnetism are the same ten billion light years away as here. The spectra of those quasars are recognizable only because the same chemical elements are present there as here, and because the same laws of quantum mechanics apply. The motion of galaxies around one another follows familiar Newtonian gravity. Gravitational lenses and binary pulsar spin-downs reveal general relativity in the depths of space. We could have lived in a Universe with different laws in every province, but we do not. This fact cannot but elicit feelings of reverence and awe.
We might have lived in a Universe in which nothing could be understood by a few simple laws, in which Nature was complex beyond our abilities to understand, in which laws that apply on Earth are invalid on Mars, or in a distant quasar. But the evidence – not the preconceptions, the evidence – proves otherwise. Luckily for us, we live in a Universe in which much can be ‘reduced’ to a small number of comparatively simple laws of