"What is life?" is a question that theoretical biologists are trying hard to figure out. Physicists have even entered into this field of inquiry. There are no definitive answers as of yet, but the question of how to get these answers persists. Can science ever understand what life is? I will look at two different views of how we are going to arrive at these answers, if possible; one based on a tradition of science from one of these physicists turned theoretical biologist, and one from a new science emerging (how ironic) from the biological tradition only to try and flip the views on their heads. The former being Erwin Schrödinger in his infamous and well-noted essay entitled aptly What is Life? and the latter being a proponent of artificial life Christopher G. Langton in his essay entitled also very pertinently Artificial Life. Schrödinger takes the traditional reductionist view of life, while Langton takes a view that, instead of going top down, goes from bottom up. Are these methods going to answer the question to what life is, or is science getting in over its head on this question? I will argue that these methods have added greatly to the study of science and what features life might have but they remain unable to answer the question – "what is life?"
Erwin Schrödinger is famous for his piece because of his new paradigm of the "code script" that leads to many advances in modern biology, including the discovery of the double helix of DNA. These advances give credibility to the reductionist method, one that almost every science uses. He asks, "Can we trace back this state of affairs to some kind of first principle, in order to ascertain and to understand why nothing else is compatible with the very laws on nature (pg. 3)?" And his answer is "The answer to all the queries is in the affirmative (pg. 3)." Schrödinger is taking a most defiantly reductionist stance.
Schrödinger enters biology tip-toeing, however, by calling himself the "naïve physicist" as he tries to tackle a discipline he is not a master of. But he does notice somewhere the biologist can start from – the "code script". He wants to pen this down as the "all-penetrating mind … to which every causal connection lay immediately open… (pg. 4)" This is the key for Schrödinger. It seems that if we knew what was going on inside the "code script" we can know if the "egg would develop, under suitable conditions, into a black cock or into a speckled hen… (pg. 4)" The reductionist will find the answers the further in it goes. This attitude, of the "code script" being the answer to life (or something much closer, at least) is what drove many scientists to work heavily in that area, like Watson and Crick who later found the double helix of DNA. It cannot be refuted that this piece, and the "code script" idea, were great motivators for investigation and discovery in biology in the years after this piece was published. Is that it? Is that going to answer everything, once we know how the "code script" works?
Schrödinger takes what he has learned from quantum physics and sees parallels in biology. He points out mutation as one; he calls it the "quantum theory of biology (pg. 6)" figuratively. If this is the case then he understood that the "code script" just might not be the end of the road. He admits that he was looking for new laws of nature when coming to this field and has discovered that it gives nothing in that direction. Biology, he finds, does not offer new laws of nature, it only offers more questions. He points out that living organisms don't react according to the statistical physical laws, but that doesn't mean they don't follow some order. Although he admits, "from all we have learnt about the structure of living matter, we must be prepared to find it working in a manner that cannot be reduced to the ordinary laws of physics (pg. 9)," he is unwilling to admit that perhaps reductionism might not be the way to gain these answers. I don't blame him, however, because this paradigm is far stronger than any we have seen in science.
Schrödinger points out several things that might not be answerable by reductionism in his own paper, like the "jump-like" mutations, which he parallels with quantum theory. He points out why it should be a rare event, so the mutation has a chance to be tested out without other mutations at the same time throwing off the 'test' as it were. But these are not linear things in a species, they cannot be "traced back" as he said before. These things react to the environment, which is where the 'test' is decided good mutation or bad mutation. Admitting that seems like admitting that we won't know the cause until we understand the environment, which he makes no claim about. He purports that the mutation is inherited perfectly by its offspring and that's it. This gives us nothing about the environment and adaptation to it. He continues to bring up quantum theory but pays no attention to the problems with that analogy. He agrees that at the level of the cell it seems unpredictable but correlates that to the statistical physical laws that make order apparent at the macro level, examples being dissipation. We cannot predict one molecules movement in water but we can predict that all of them will dissipate. This idea gives us our stability in life, but he admits to the atomic level (namely genes, or this "code script") effecting out lives on the macro level, namely mutations. So, how is it that he can hold that the small things are unpredictable (like in physics) but they follow some orderliness at the macro level: and at the same time that the micro level effects so much change in our systems (mutation)? It would seem that he is really saying that what evolution is based on, mutation and adaptation, is totally unpredictable, and yet he feels that we can reduce life to some "code script" in our systems still.
Is there any other way of finding answers? Christopher Langton is working on that. If reducing down isn't the method that you feel will work, what else is there? Langton wants to study methods of creating life that might help us understand what life is, he says, "biology is the scientific study of life on earth based on carbon-chain chemistry (pg. 1)." But what about non-carbon based life, isn't it possible? Langton argues that it is "impossible to derive general principles from single examples (pg. 1)." This is his worry of reductionism; if we are focusing on life on earth, which has a common ancestry according to evolutionary theory, then we are dealing with just one (or few) examples of 'life'. Reducing an engine from a Corvette is not going to explain how all vehicle engines work. Going top down is a problem because even if we could find out what living organisms on earth were constructed of we only know about "life-as-we-know-it" when we should be studying "life-as-it-could-be". Philosophically speaking, this is where it gets interesting. What are the possibilities of life, not just what happened to evolve on this planet? If we don't worry about the universals then we aren't really attacking the question of 'life', just life on earth. Artificial life studies are attempting to create organisms or programs that we might call living. Instead of just studying the mechanics of life, we must study the dynamics of life.
Langton understands the interaction of things is important. Creating life with all the elements intact will give us a picture of how life reacts to things and situations. One might say that as soon as a reductionist takes an organism out of the environment to study it they have just killed it, or are already missing a piece of the puzzle. Langton argues that life is a non-linear system, basically, non-predictable. If life were linear we might be able to "trace back this state of affairs to some kind of first principle," as Schrödinger stated. But non-linear systems are by definition unpredictable, and as such, are impossible to trace back. However, Schrödinger agreed, even if he didn't know it, that living organisms need the environment in order to even exist, which is why he talked about testing a mutation. The environment needed to react to the organism like the organism needed to react to the environment after a mutation in order to evolve and adapt. Schrödinger wasn't connecting the environment like Langton was and therefore missing the important distinction between linear and non-linear systems. He was still allowing the study of life in a vacuum in order to reduce down to cellular structure, genes, nucleotides, etc… but not acknowledging the interaction, synthesis, of these things with the environment. He was working on analytically deducing: Langton wants to worry about the dynamics of it all. It remains impossible to study in the reductionist manner when we are studying a non-linear system, so this is why Langton wants to argue for the AL study method of bottom up.
What about the operations of life? This is where Langton gets a bit confusing. He mentions that "Enzymes are the functional molecular 'operators' in the logic of life (pg. 8)." After all the talk of synthesis, he returns to the classic, linear, model of how DNA works. He says the genes are expressed through the mRNA strand that then turns into proteins and maybe enzymes. It seems even he can't resist having a single thing that reigns supreme in life. Of course does he know if enzymes are the major player in non-carbon-based life? But what about the "RNA world" idea? This states that RNA was before DNA, and thus can exist without its information. Also, we are now finding out that the genes aren't in a one to one match with phenotypic results. For example, 'The' gene for hair color could be over lapped with the gene for pointed ears, and/or be activated by its position to other genes in the DNA strand. His relation from genotype to phenotype is still accurate; however, "The phenotype is a non-linear function of the genotype (pg. 9)."
What all this boils down to is that we know very little about what life is. I think Schrödinger; with his "code script" metaphor helped many scientists discover what they discovered after his essay, and thus, contributed to the tradition, and reliability, of reductionism in science. However, Langton makes a strong argument to why that can only get us so far. We can only learn about life as we know it on earth, but never come close to 'life' in more of a Platonic form idea; philosophically speaking, without understanding the dynamics of life and its surroundings. Would you exist without the environment you live in, regardless of your genetypical or phenotypical traits? But the fact remains that AL work has not created this life as of yet. There is a new area of research that is taking on similar challenges without creating life called systems biology. They ask the holistic question of life and leave off the study of the mechanics.
Will this solve the problem? I don't think so. I don't think any of these fields will come close to really answering the life question. I think using Langton's idea of synthesis to weld these two methods together to find answers will get us as close as possible, but philosophically speaking, the answer to "what is life" remains a metaphysical one. Understanding what life could have been in the field of AL might help us discover whether our life forms are unique or not and even cure diseases, but not really "what is life". Decoding the 'code script' can help us read the book of evolution or our lives and even answer what features of life are unique to life, but does that answer the life question? I think Stephen J. Gould might say that this just isn't in science's Magisteria. I would agree these methods remain unable to answer the question of 'life'; the question of 'life' has only gotten more and more complex as biologists gain more and more knowledge of how life functions. It seems the harder we look for 'life' the harder it is to find anything. We may gain more knowledge of life if we manage to find it in the expanse universe, but even that would probably only muddle what we 'know' about life and make the 'life' question even more elusive.