Note: I know effecting Plato is presumptuous, but I have been listening to an excellent podcast of Plato's The Republic read by Patrick Horgan, that I thought I'd give it a try. You can get it from here if you don't have iTunes.
"I perceive, Jegonides, that you are once again lost in thought for you have not touched your grilled tuna and cold beer with the same bacchanalian efficiency as you have been known to possess," said Capricius.
"Aye, Capricius," I said. "For I have been pondering the difference between life and non-life. Take this tuna, for instance. Chemically, it is composed of the same stuff as a live tuna, and yet here it is, dead, grilled, and tasty. And this beer. Isn’t it quite curious that the yeast that transformed the malt's sugars into alcohol, despite not having eyes and ears, nor leaves and branches, are considered alive?"
"Quite honestly, I’ve never thought about it, Jegonides. It is enough that I enjoy my vittles and libation without the distractions of questions on what life is. But I'll indulge you, seeing as it is that there is an absence of ogleable babes in this establishment tonight. Let's have at it."
"Where would you say life is, Capricius? Does life reside in the living thing as part of its chemical and mechanical processes? Or is there an energy, a life-force, that resides in the living creature such that when it leaves it, the creature dies?"
"I would say life resides in the thing itself, Jegonides."
"If life resides in the thing itself, then if we take a bacterium... You do think that a bacterium is alive, don't you?"
"Good. If we take a living bacterium and examine it for its chemical composition, and take another bacterium, but this time one just dead, and examine that for its chemical composition, and if we compare the chemical composition of these two specimens, would we find anything different in their chemical composition? And if we did the same thing to a cat, and to a fish, and to a beetle, would we find a difference between the chemistry of the living specimen with the dead one?"
"I suppose we wouldn't find any difference in their chemistry," he said.
"Therefore life isn't in the chemicals, wouldn't you say so?," I asked.
"Yes," he said. "There must then be an invisible life-energy that resides in the creature that gives it life."
"Has anybody seen this energy?"
"As far as I know, no one has."
"Then how do you know it is there?"
"From its manifestations."
"In other words, life is caused by a life-energy that no one has ever seen and can only be proven by its manifestations such as the presence of life. Do you expect to--"
"I know. It is a meaningless argument. But you have to admit, it doesn't settle its truth value," he said.
"Of course. But for our purposes, such circular reasoning just won't do. It's unsatisfying." I said.
"Well what do you propose? Do you have an answer?"
"I have... a theory. I won't be so presumptuous as to say that it is the definitive answer, but I'll present it to you. See if you agree."
"The first living creatures, when they emerged, what is it about them that made them alive? What differentiated them from the non-living things?"
"Let's see... Proteins, amino acids, molecules...something that made them replicate--make copies of themselves."
"In modern living things, what is that?"
"DNA. Every thing that we consider alive has it."
"That's correct. DNA contains the instructions that our body follows to function and to keep itself alive and to reproduce."
"Therefore I was right the first time. Life resides in the thing itself. DNA is in the thing itself."
"So it would seem, Capricius. So it would seem. Tell me, are you familiar with books?"
"Don’t be ridiculous, Jegonides. Of course I’m familiar with books."
"If you take a book, let's say a book on Calculus, and you threw that book into the fire, did you destroy the Calculus?"
"Of course not. I merely destroyed the book. The Calculus isn’t destroyed."
"And if you threw, say, Hemingway's The Sun Also Rises into the fire, did you burn The Sun Also Rises?"
"No, I did not."
"Would you say then that in throwing the books into the fire, you merely destroyed the media in which they were written, and not the works contained in the books themselves? That these works continue to exist and are not dependent on the media they were written in?"
"That is precisely what I’m saying, Jegonides."
"And you are familiar I suspect with computers?"
"Jegonides, we work with computers everyday. I am familiar with computers."
"What differentiates a dead computer from a working computer?"
"A power source, I suppose. If you pull the plug on a computer, it will cease to function."
"Yes, yes. But not all computers need to be plugged. Let's say you have two computers, both running on batteries and therefore do not need to be plugged, what differentiates a working one from a dead one? When do we call one working, and the other a piece of refuse?"
"We call one working when it is able to run the software in it."
"And what do we call a computer that cannot run any software?"
"We call it dead."
"And this software, where is it? Is it in the computer?"
"Yes it is."
"It is in the computer such that if you throw the computer into the fire, you destroy it?"
"Wait. I see where you’re going. The software is not destroyed. I merely destroyed the medium the software was written in but the software itself continues on."
"Splendid. So where is it? Does it exist merely in our mind, in which case it has a subjective existence? Or does it exist outside our minds?"
"Outside our minds. It certainly isn’t subjective."
"If it exists outside our minds, where is it?"
"I do not know. But it certainly exists, or else none of our computers would run."
"Yes, precisely. You don’t know where it is because, even though it exists, it isn’t located anywhere. It is pure information. I submit to you, dear Capricius, that such is the same for the information in our DNA. DNA is merely the medium in which it is written. The information in the DNA itself exists nowhere. And if the body fails to access the information in the DNA for whatever reason--through trauma or entropy--it ceases to function, and is for all intents and purposes, dead."
"So you’re saying information is the difference between life and non-life. And information isn’t in the body, but is accessed through the DNA which contains the information."
"That's exactly what I’m saying, Capricius. I submit that life is hardware that is able to access a software, is able to power itself, is able to reproduce. Would you agree?"
"I would add, life must be able to react to the environment, and must come from nature."
"Very well. Is your computer alive?"
"No it isn’t. It cannot reproduce."
"I submit that it can reproduce, Capricius."
"Don’t be absurd, Jegonides. My computer cannot reproduce."
"It can and it does. Tell me, are there any other computers like yours?"
"Yes. It's a very popular model."
"Where was it made?"
"In the factory, of course. A factory that makes computers."
"There you go. It is able to reproduce in a factory. A factory gives birth to it, so to speak."
"Don’t be silly. It has to be able to reproduce by itself to be considered alive."
"A worker ant can't reproduce by itself. It needs another vector, another entity, namely the queen, to reproduce. Yet I’m sure you do not doubt for an instant that it is alive."
”Yes but a queen ant is an ant. A factory is not a computer.”
“Beside the point. A queen ant is an entity that contains instructions and tools on how to make more ants. That the factory does not look like a computer is not important. If for example the architect designed the factory’s building in such a way as to look like a computer, would you withdraw your objection? Now both computer and factory look alike.”
“You’re incorrigible. Besides, humans work in the factory to make the computers. A living thing ought not to have help from another species to be considered alive.”
“Certain plants can only reproduce through the help of insects. Some orchids for example can only reproduce through pollination by wasps, which they then reward with nectar. Are you doubting that the orchid is a living thing?”
“Of course not.”
“So the help of other species does not disqualify a being from being considered alive. ”
“But a living thing is composed of organic chemicals. My machine is not,” he said.
“Chemicals,” I said. “Your machine is composed of chemical elements. What a thing is made of ought not to disqualify it from being called alive. What if in another planet, living creatures were made of different stuff? Surely, if life evolved here, and used organic chemicals because of its abundance, life elsewhere could evolve from chemicals that have the same properties and is in abundance there.”
“Ah but my computer cannot react to outside stimuli. It just sits there. It cannot regulate its own bodily functions. Therefore it cannot be considered a living thing.”
“That’s true. But if it can? Say, if it has sensors that sense outside temperature and a mechanism in it that regulates its working temperature such that it keeps itself within that optimum working temperature, and if it has software running in it that tells the computer what to do should the temperature go up or down, or whether an environment it is in contains chemicals which could be harmful for its parts, that it should sense it and stay away? Or that it has light receptors that tell it when it is light out or dark that it can then select whether to turn its light on? Or that it can perform complex tasks such as gathering data and send it to another machine? You admit that such a machine can exist?”
“Yes such a machine can exist, I suppose. But a living thing draws energy from its environment.”
“That objection can be solved by equipping your machine with a solar battery that draws and stores energy directly from the sun as plants do.”
“And growth? What about growth? A living thing grows, Jegonides.”
“Not all do. Bacteria divide into fully formed entities. They don't go through a childhood stage.”
“Mobility then. A living thing is mobile. Even a plant extends roots and leaves.”
“So if your computer had wheels, it can be mobile. In fact with the proper software like those in modern cars, it can adjust its traction and which wheels get the more power based on the terrain.”
“But we know who made my machine. Humans made my machine, or at least the factory that made my machine. Anything made by humans can’t be alive.”
“Why not? You believe in God, do you not? So if we were made, why can’t what we make be considered alive? Both us and the machines we make, the kind of machine we’ve been talking about are both manufactured.”
“We arose from nature. Nobody made us. A living thing ought to arise from the laws of nature, whatever those laws are. Evolution for instance.”
“Are we part of nature, Capricius?”
“Therefore anything that is the work of our hands also comes from nature since we are natural agents. If we evolved, we evolved abilities that made us capable of making things, and I submit some of these things can be considered living things based on our definition of what it means to be alive. Your computer was made by nature because it was made by man.
“To reiterate, Capricius, we have agreed that a thing can be considered a living thing if it can reproduce, can react to its environment, can draw energy from the environment, is mobile, and comes from nature. These criteria can be satisfied, not by your computer, but something else. A different machine. One that exists even as we speak. I’m talking of the Mars Rover.”
“So there is life on Mars, Jegonides.”