What is life?
Living beings were once thought to be composed of an entirely different substance from that of non-living things. However, we now know that both forms of entities are the same, at least at the molecular and atomic levels. Trees, rocks, cars, elephants, human beings – we are all made from the same material. So what differentiates life from non-life? At what level of complexity does a group of molecules and atoms become a living entity?
With the ancients, we divide the world into living and nonliving beings, but have no widely accepted meaning of the word ‘life’. Organisms are composed of cells that are composed of molecules that are composed of atoms, and it is not clear at what level of complexity life first emerges. The cell is a miracle of the physical world and required billions of years to evolve; can we say that it is nonliving and claim that life must exist in complex multicelullar organisms? Living organisms grow, move, reproduce, and behave in response to their environments. Many nonliving things exhibit similar properties. An automobile moves and consumes food; a crystal grows; a candle flame needs nourishment, reacts to its environment, and self-reproduces with sometimes alarming consequences. Computers play chess with each other and are taking control of more and more of the routine functions of society. With so many nonliving things mimicking the characteristics ascribed to living organisms, it is difficult to know exactly what defines life. Nothing of a physical nature sets life apart from the rest of the physical world. ~ Edward Harrison, Cosmology: The Science of the Universe
On one extreme, we have the reductionist view that the entire complex world around us can be broken down into smaller and smaller constituents. Life (and even consciousness itself) is nothing more than particles interacting with one another on the physical level. There is nothing more to it. Whatever illusion we have of the Mind and free-will, are determined by physical processes at the subatomic level. Then there are those that believe that life and Mind cannot be explained through such reductionism, and that new ‘phenomena’ (for lack of a better word) emerge as the level of complexity increases. On the other extreme end, there are the Vitalists who believe that life and consciousness are essentially non-physical. There is this ‘breathe of life’, or ‘psyche’ that permeates the physical world and animates it.
Life, viewed objectively, seems sufficiently explained in terms of organic structures and their functions. Viewed subjectively, however, its inner world of experience seems inadequately explained by its own concepts of the physical world. No instrument in the laboratory can detect the existence of consciousness and yet each of us knows that consciousness exists. ~ Edward Harrison, Cosmology: The Science of the Universe
How did life originate on Earth?
An old view was that life was spontaneously created all the time – worms in the earth, maggots in corpses and apples, flies around waste. That was until Francesco Redi discovered that maggots were born from eggs laid by flies, and Louis Pasteur discovered how the generation of microorganisms could be avoided by isolating them from the atmosphere, proving that they spread through the air. Panspermia theories propose that life on Earth originated from space, spreading from planet to planet and thriving where conditions were suitable. So it is only a transport theory rather than a theory of origins. In biochemical theories, molecular processes obeying the laws of physics eventually formed self-replicating systems that continued to grow in complexity until natural selection took over and life as we know it arose. This is now the most preferred scientific view of the origin of life. Of course, there are still those who believe that a Supreme Being created life in all its present forms in an act of special creation a few thousand years ago.
Is there life elsewhere in the universe? What about intelligent life?
The answers to these questions remain holy grails in science. From ancient times to the present, we have never stopped speculating.
It goes against nature, in a large field to grow only one shaft of wheat, and in the infinite universe only one living world. ~ Metrodorus, a student of Democritus
Nothing in the universe is unique and alone, and therefore in other regions there must be other earths inhabited by different tribes of men and breeds of beasts. ~ Lucretius, De Rerum Natura
The universe is a pretty big place. It’s bigger than anything anyone has ever dreamed of before. So if it’s just us… it seems like an awful waste of space. ~ Dr. Arroway in the movie ‘Contact’, based on Carl Sagan’s book with the same title
It will be interesting to speculate on how the discovery of extra-terrestrial intelligent life will affect Christian theology as well as other religious faiths. It’s true that the Bible has nothing to say about life on other worlds, but it will be naive to pretend that the discovery of E.T. will not be problematic for Christianity. Does the Christian story of the incarnation of Jesus and the redemption of creation involve only the earth and not the entire cosmos? Does this then reduce the significance of Jesus? Are there other incarnations and other ‘Saviours’? What if these E.T.s have no concept of God or morality? What’s surprising is that the Vatican has pre-empted such discoveries, and has gone one step ahead by convening a conference on astrobiology that includes notables such as Paul Davies and SETI director Jill Tarter.
If the evolution of life is seen to be almost inevitable, the atheists say that naturalism reigns and there is no need for a Creator, while the theists say that God has so beautifully ordained the order of nature that creation is indeed able to make itself. If life is so rare as to make its occurrence on earth seem a fortuitous event, the atheists say that it shows that humans have emerged by chance in a world devoid of significance, while theists are encouraged to see the hand of God behind so fruitful but unpredictable an occurrence. Science influences metaphysical understanding but it certainly does not simply determine it. ~ John Polkinghorne, Science and Theology