We can grant that pleasure is indeed a good thing, though we will want to distinguish higher from lower pleasures and subject the notion of pleasure to some scrutiny. But the problem is that being alive can be worthwhile in the absence of pleasure. If my pleasure centers are destroyed, is my life thereby rendered totally worthless?
What if our Martians were antihedonists who had abolished pleasure from their lives long ago—can they now be slaughtered without scruple? So it is not pleasure alone and as such that confers value on life. Might we make more progress if we acknowledged a continuum of value to lives? And do we really want to say that some human lives are more valuable than others? Do some humans have more of a right to their life than others?
But maybe we can steer clear of these ethical shoals while accepting that what makes life good can come in degrees, even if everyone who meets the condition has a nonnegotiable right to life.
And let us not forget those unconscious zombies—they must be included too. They are all alive, to be sure, but what is it about their ontologi- cal condition that makes their aliveness amount to something good? As I said, I am really not sure, but here is a thought to play with: they all have knowledge.
Knowledge is something that can come in different kinds and quantities in different creatures, and hence can confer different degrees of goodness. These are the basic capacities of any minded creature though not total zombies that lack even an unconscious mind , so there is not much danger of chauvinism.
The question is going to be whether, and in what sense, knowledge in this capacious sense is good. Certainly, it is traditional to regard knowledge as an intrinsic good, and intuition resonates to the suggestion; but we need to say more about what its goodness consists in. It sounds rather feeble to say that it consists in having true justified beliefs: why is that thought to be so life enhancing? What has knowledge in that sense done for you lately?
One point that has been made is that knowledge is enriching: it adds to the form and quality of the self, it enlarges the self, it connects the self to what lies beyond its solitary confines. But it is not terribly clear why this is supposed to be such a good thing: eating a lot enlarges the self too, and connects the self to the world beyond, but obesity is not generally thought to be what makes being alive worthwhile.
The enlargement has to be of something recognized to be good in itself. It might be suggested that knowledge increases understanding and empathy, but here again we run the risk of excluding the less exalted kinds of life, as well as raising questions about those putative values. Mere cognitive contact with things seems a slim basis on which to erect a theory of the value of life. We are in distinct danger of showing that there is nothing that makes being alive good, in the sense in which we seem to mean it.
Maybe this is just a false belief that the genes have installed in us for their own selfish reasons—like the belief that there is something especially meritorious about our kin as opposed to strangers. There are worthwhile things that are effects or correlates of life—such as pleasure, beauty, virtue, and accomplishment—but being alive itself seems to lack any inherent value.
Why is it so valuable that an owl can see things with great acuity putting aside its utility in catching prey? Why is my ability to be aware of the position of the sun so crucial to the value of my life? What is so good about knowing of terrible tragedies? Here is a suggestion: knowledge gives point, not to the living knower, but to reality outside of the living knower. It is not that human life would be meaningless without knowledge but that the universe would be meaningless without it.
Because such a property does not exist. Life is a concept that we invented. On the most fundamental level, all matter that exists is an arrangement of atoms and their constituent particles. These arrangements fall onto an immense spectrum of complexity, from a single hydrogen atom to something as intricate as a brain.
In trying to define life, we have drawn a line at an arbitrary level of complexity and declared that everything above that border is alive and everything below it is not. In truth, this division does not exist outside the mind. There is no threshold at which a collection of atoms suddenly becomes alive, no categorical distinction between the living and inanimate, no Frankensteinian spark.
We have failed to define life because there was never anything to define in the first place. I nervously explained these ideas to Joyce on the phone, anticipating that he would laugh and tell me they were absurd.
After all, this is someone who helped NASA define life. The working definition was really just a linguistic convenience. Carol Cleland , a philosopher at the University of Colorado Boulder who has spent years researching attempts to deliniate life, also thinks that the instinct to precisely define life is misguided—but she is not yet ready to deny life's physical reality.
A photo taken with an electron scanning microscope of the ALH meteorite, which supposedly formed on Mars 4 billion years ago before eventually reaching Earth. A handful of scientists think the chain-like structures in the photo are fossilized Martian nanobacteria, but most researchers are skeptical Credit: NASA, via Wikimedia Commons. What we really need, Cleland has written , is "a well-confirmed, adequately general theory of life.
Before scientists understood that air, dirt, acids and all chemical substances were made of molecules, they struggled to define water. They could list its properties—it was wet, transparent, tasteless, freezable and it could dissolve many other substances—but they could not precisely characterize it until researchers discovered that water is two hydrogen atoms bonded to an oxygen atom. Whether salty, muddy, dyed, liquid or frozen, water is always H20; it may have other elements mixed in, but the tripartite molecules that make what we call water water are always there.
Nitric acid may resemble water, but it is not water because the two substances have different molecular structures. Creating the equivalent of molecular theory for life, Cleland says, will require a larger sample size. Imagine trying to create a theory about mammals by observing only zebras. I disagree. Discovering examples of alien life on other planets would undoubtedly expand our understanding of how the things we call living organisms work and how they evolved in the first place, but such discoveries would probably not help us formulate a revolutionary new theory of life.
Sixteenth century chemists could not pinpoint what distinguished water from other substances because they did not understand its fundamental nature: they did not know that every substance was made of a specific arrangement of molecules. In contrast, modern scientists know exactly what the creatures on our planet are made of—cells, proteins, DNA and RNA.
What differentiates molecules of water, rocks, and silverware from cats, people and other living things is not "life," but complexity. Scientists already have sufficient knowledge to explain why what we have dubbed organisms can in general do things that most of what we call inanimate cannot—to explain how bacteria make new copies of themselves and quickly adapt to their environment, and why rocks do not—without proclaiming that life is this and non-life that and never the twain shall meet.
Recognizing life as a concept in no way robs what we call life of its splendor. It's not that there's no material difference between living things and the inanimate; rather, we will never find some clean dividing line between the two because the notion of life and non-life as distinct categories is just that—a notion, not a reality.
Everything about living creatures that fascinated me as a boy are equally wondrous to me now, even with my new understanding of life. I think what truly unites the things we say are alive is not any property intrinsic to those things themselves; rather, it is our perception of them, our love of them and—frankly—our hubris and narcissism.
First, we announced that everything on Earth could be separated into two groups—the animate and inanimate—and it is no secret which one we think is superior. Then, not only did we place ourselves in the first group, we further insisted on measuring all other life forms on the planet against ourselves.
The more similar something is to us—the more it appears to move, talk, feel, think—the more alive it is to us, even though the particular set of attributes that makes a human a human is clearly not the only way or, in evolutionary terms, even the most successful way to go about being a 'living thing. Our late family cat, Jasmine Credit: Jabr family. Truthfully, that which we call life is impossible without and inseparable from what we regard as inanimate.
Detecting alien life is a harder task than collecting samples, however, as illustrated by the Viking mission. In , NASA put landers on Mars and performed a variety of experiments to try and detect signs of life in the Martian soil.
The results were inconclusive: while some tests returned positive results for the products of chemical reactions that might indicate metabolism, others were negative for carbon-based organic molecules.
Decades later, astrobiologists are still limited to looking for life indirectly, searching for biosignatures -- objects, substances or patterns that might have been produced by a biological agent. Given that scientists who look for life are fine with signatures, some say we don't actually need a definition. According to philosopher Carlos Mariscal and biologist W Ford Doolittle, the problem with defining life arises from thinking incorrectly about its nature.
Their strategy is to search for entities that resemble parts of life and to think of all life on Earth as an individual. That solution might suit astrobiologists, but it wouldn't satisfy people who want to know whether or not something strange, like a virus, is alive. A major challenge for both detecting and defining life is that, so far, we've only encountered one example in the Universe: terrestrial life.
If we can't even agree on the distinction between living and non-living things, how can we expect to recognize weird forms of life? As science hasn't provided conclusive proof of extraterrestrials, we must turn to science fiction, and few series have explored such possibilities better than Star Trek: The Next Generation. The voyages of the starship Enterprise and "its continuing mission to explore strange new worlds and seek out new life and new civilizations" gave us everything from the god-like being Q to a huge Crystalline Entity that converts living matter to energy a kind of metabolism.
Perhaps most interestingly, as researchers get closer to creating an artificial intelligence that's smarter than a person, there's Data -- an android who had to prove human-like sentience but didn't reproduce until he built his own daughter. Would a god who exists beyond time, a spaceship-sized crystal or a robotic AI be considered 'alive'? And the answer is complicated by the fact that researchers from different fields have differing opinions on what they believe ought to be included in a definition.
Philosopher Edouard Machery discussed the problem and presented it as a Venn diagram with circles for three groups -- evolutionary biologists, astrobiologists and artificial-life researchers -- using hypothetical features upon which they would converge some biologists think viruses are alive while others believe the cell is essential, so assuming members would agree is controversial. Machery claimed that no criteria could fall within the overlap of all three circles, concluding that "the project of defining life is either impossible or pointless.
But while philosophers can sidestep the problem without consequences, the conclusion that it's futile to define life is both unsatisfying and frustrating for regular folk and also for those like me, who care about the public understanding of science. Regardless of whether researchers ever reach a consensus on a scientific definition, we still need a folk definition for practical purposes -- a sentence to explain the concept of life that the average person can understand.
Life may be a fuzzy concept, but that doesn't mean its meaning should be vague. As computational biologist Eugene Koonin pointed out , defining life isn't scientific because it's impossible to disprove, as we can always find an entity that meets all criteria but is 'clearly' not alive, or lacks certain features but is 'obviously' a life-form, and so "some kind of intuitive understanding of the living state superseding any definition is involved [ We live because others want us to, and we want them to live along with us.
We live because we have hope, and want to see what happens next. I hope that lots of people live because they know life at its best can be wonderfully good, and want to help make it so: and that is a great reason for living.
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