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Recently I was fixing a broken clock,1 and that set me thinking about things that move by themselves but are not actually alive. The biological definition of life is quite exact: what differentiates animals, plants, fungi, and microbes from inorganic materials, even those of complex and exquisite design that happen to move—a leaf blowing on the wind, for example—is that living things can grow, change, sustain themselves, exhibit functional activity, react to their environment, reproduce their own kind, and eventually die. The broken clock, aside from once exhibiting functional activity and now an apparent state of death, does none of these things.
Definitions are tricky things, however. They are trying to put a precise meaning in words to a state which can easily be understood by observation and sensed in the gut, but which may be a slippery thing for the intellect to grasp. For example, many people I know have not reproduced themselves, being childless. Many people in a vegetative state cannot sustain themselves or even react to their environment. Many more people may grow and change in the barest organic sense, but not in any intellectual, emotional, or spiritual capacity. And finally, death is not proven for any of us—especially now, with more new medical techniques being developed every year—until it actually comes. So, are these cases of people who are, according to the definition, not alive?2
Modern advances in robotics and cybernetics are going to test that definition of life even more stringently. A software program can be reproduced quite easily, and it’s no stretch of the imagination to think of a program with the right internal commands—let alone the volition of an artificial intelligence—that can replicate its own code, package the result, and send it down the line into a new computing environment.3 So, would such a program qualify as alive under at least one parameter of the biological definition?
Software fulfills other specifications for life as well. Depending on the type of code, it certainly exhibits functional activity, can grow and change, and can react to its environment in the form of received inputs and commands and internally generated outputs and displays. One might argue that a piece of code cannot sustain itself without a computer’s central processor, memory chips, storage space, and the electricity to run these bits of hardware. But then, a human being cannot sustain him- or herself without the environment of a suitable planet or space station, externally provided pieces of hardware in terms of clothing, furniture, tools, entertainments, and other comforts, and the food—generally grown and processed by others and shipped over long distances—required to sustain the human organism.
The fact that the software has required—at least initially—a human mind and human invention to create both the code and the machine on which it runs has no bearing on the definition of life. After all, humans did not create the planet on which they live, the solar energy that drives its climate and crops, or the air they need to breathe. And humans did not create themselves from first principles, either. Questions about a creator god, or the origins of the organic chemical reactions necessary to promote molecular biology, are outside the biological definition of life.
So life according to the old biological definition may be complete for animals and plants, but insufficient to encompass the new world that technology is making for us. And it may not be sufficient for all the types of beings we might find out among the stars.
If you asked me to create an iron-clad definition of life, suitable for all purposes, I would strip the biological definition down to its barest chassis. Life is an open-ended process, reflecting functional activity that is usually, but not always, carried out by an underlying mechanism employing material substances which interact through energy inputs. And that process must be susceptible to interruption and cessation.4
Under these terms, an artificial intelligence operating on a computer chip or inside a robot could be considered alive. So could an automated factory or a fire engine. Questions about volition, free will, or freedom of action and movement are outside my stripped-down definition of life, as they are for the biological definition. After all, clams, mussels, and corals are all alive and yet have no volition or free will to do other than settle down on a rock or in the sand and perform the filter-feeding for which their bodies were designed. A domesticated horse that lives in a stable, gets hitched to a plow or wagon everyday, and eats what, when, and where its human owner directs is hardly able to exercise its innate volition. And humans who are enslaved or under the psychological domination of another person have vastly diminished capacity for free will and freedom of action.
In my definition, the difference between a horse and a fire engine is that the horse can refuse the orders of its master, can fight the bit, shy back from the harness, and balk at the feedbag. The slave can decline into a psychological depression, lie down, and choose to die. But the fire engine goes where its driver directs—even if that means plowing into a brick wall at sixty miles per hour. But exercise of free will is still not part of the definition of life.
When we go out among the stars we are going to find many strange and wonderful things, and not all of them will be in their first flower of growth and development. We will discover decaying worlds full of automated machinery and robots, either waiting dormant or still actively functioning, but left over from the organic civilizations that invented them, perfected them, used them, and then died out either slowly or rapidly, leaving them behind. We will discover slave cultures whose biology, capacities, and expectations were manipulated into a state of perfection—perfect in terms of what the manipulators desired as to nutritional requirements, mental and physical capacities, and personal direction and volition—and then left to collapse or evolve on their own when the master race died out.
And note that in my stripped-down definition I added “but not always” to the part about an underlying substantive mechanisms. This allows for the sort of life forms made of pure energy—presumably, once-organic creatures who have surpassed their physical bodies and become pure spirit—that are found in much of science fiction.5 Who is to say that patterns previously established in the electrochemical circuitry of neural nets or the silicon pathways of chip sets might not reform and propagate outside those physical structures? Certainly, self-sustaining electrical circuits are not known in our definition of physics. But we know that radio waves propagate in complex patterns of photons outside any conducting aether or physical fluid. And who is to say that our definition of physics is so very complete?6
Perhaps one day we will discover that leaves blowing on the wind do have minds of their own.
1. No, not fancy clockwork filled with gears and springs, as in the picture—that’s just to draw your attention. I am not that mechanically gifted. Instead, it was one of those black boxes with a three-layered drive shaft and place for a Double-A battery, which then fits through any fancy clockface as part of an art project. But the principle is the same: as an object with its own functional activity, the little black box had stopped working.
2. I know, I’m treading the distinction between group characteristics of the species Homo sapiens and the individual characteristics of a John or Jane Doe. But the definition of life is also generally stated without making such a distinction.
3. That’s the basis of my early novel ME: A Novel of Self-Discovery. But you don’t have to look to fiction for self-replicating software: tapeworms, viruses, and other malware do it all the time—and with a persistence and tenacity that mimics life itself.
4. I’ve thrown in the notion of death just so we don’t have to consider the roiling plasma inside a star as some kind of life form. And come to think of it, every star grows, changes, is self-sustaining—so long as its gravity and its fusible elements remain in proper proportion—and eventually it dies out with either a bang or a cinder.
5. Not to mention a few gothic horror and ghost stories.
6. See Three Things We Don’t Know About Physics (I) and (II) from December 30, 2012, and January 6, 2013.