# What defines life? **URL:** \ **Category:** Great Debates\ **Created:** [January 18, 2006, 9:05pm UTC](https://boards.straightdope.com/t/what-defines-life/340557 "2006-01-18T21:05:41Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 19, 2006, 5:10am UTC](https://boards.straightdope.com/t/what-defines-life/340557/21 "2006-01-19T05:10:18Z")
> [@sleestak](#): > > Then obviously humans are not alive because humans require all kinds of other species (like trees) to reproduce. To reproduce humans must be alive. To live humans require oxygen. The oxygen comes from plants. The plants require the sun, earth and a whole lot of other things to produce the oxygen. Therefore humans are not alive because humans cannot live without the hosts (earths)help. Which is absolute nonsense. I am glad to see that we have reached agreement. Your argument that an organism isn’t alive if it requires assistance from other organism to reproduce is total nonsense. > [@](#): > > It seems to me that you are confusing what a life form requires to live with whether or not that it is actually alive. No, you are now begging the question. You are trying to establish that you have an objective definition of what ‘actually alive’ is. You can’t use your own inability to to distinguish between being ‘actually alive’ and simply ‘living’ as support that your definition is workable. > [@](#): > > The fact that a tapeworm requires a human hormone to live is irrelevant to whether or not it is alive. Humans require oxygen. Does that mean that humans are not alive? No, we’ve already established this. Your definition that states that requiring such help renders an organism non-living is nonsense. > [@](#): > > You speak of us being vague by using the term ‘something’ then pop out with this: That’s; right. It was intended to demonstrate just how vague and all-encompassing ‘something’ is. > [@](#): > > What actions, exactly, do DVDs undertake to reproduce? I have said it at least 5 times already. It produces pleasurable sensations in the host that induce the host to assist it in reproducing. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [January 19, 2006, 10:15am UTC](https://boards.straightdope.com/t/what-defines-life/340557/22 "2006-01-19T10:15:58Z")
Like _any_ other word, the word “life” can be argued over as to which things fall in its set and which don’t. Human language _necessarily_ evolved this way, and I’m often puzzled by suggestions that, because some entities fall on the threshold, then the entire _science_ of life is somehow impugned. Nevertheless, my own preference is that of [Francisco Varela](http://en.wikipedia.org/wiki/Francisco_Varela): > [@](#): > > **life** : an autopoietic (self-producing), water based, lipid-protein bound, carbon metabolic, nucleic acid replicated, protein readout system This effectively defines _cells_ (and anything _comprising_ cells), and thus includes mules and prokaryotes but excludes viruses, memes, robots/computer memories, fire, or other traditionally tricky-to-classify entities. One small difficulty it throws up is that “death” becomes rather a _statistical_ threshold: if you chop my head off, ‘I’ am dead (_ie._ my brain is irreparably unplugged such that it will never function as a whole organ again), even though the cells of my brain only _gradually_ fall out of the definition. Even years later, one could point to my decomposing corpse and say “there is life there”, just as one could point to me _now_ and say “there is death there”. ---
**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\ **Post date:** [January 19, 2006, 11:16am UTC](https://boards.straightdope.com/t/what-defines-life/340557/23 "2006-01-19T11:16:09Z")
> [@](#): > > **life** : an autopoietic (self-producing), water based, lipid-protein bound, carbon metabolic, nucleic acid replicated, protein readout system It seems unwise to me to exclude sytems based on other chemistries as even a hypothetical possibility. I wonder if something like “any system capable of undergoing evolution by natural selection” would work? ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [January 19, 2006, 11:28am UTC](https://boards.straightdope.com/t/what-defines-life/340557/24 "2006-01-19T11:28:05Z")
> [@MEBuckner](#): > > It seems unwise to me to exclude sytems based on other chemistries as even a hypothetical possibility. I wonder if something like “any system capable of undergoing evolution by natural selection” would work? Well, then you effectively allow computational entities and the like to live, and run into all kinds of difficulties with _individual_ entities since ‘evolution’ is only seen when viewing _multiple_ individuals - coelacanths are still _alive_ even though they haven’t evolved much (via natural selection or otherwise). Heck, one could even argue that _clouds_ evolve according to the limits set by natural environment. Carbon-chauvinistic it may be, but I’ll take this IMO tiny flaw when compared to the major defects in other definitions which bring more absurd things to life than a Wes Craven movie. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 19, 2006, 11:31am UTC](https://boards.straightdope.com/t/what-defines-life/340557/25 "2006-01-19T11:31:28Z")
> [@MEBuckner](#): > > I wonder if something like “any system capable of undergoing evolution by natural selection” would work? Nope, because then we have to accept that memes are alive, and that computer viruses are at least potential alive. ---
**Author:** ![Spatial\_Rift\_47](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Spatial\_Rift\_47](https://boards.straightdope.com/u/Spatial_Rift_47)\ **Post date:** [January 19, 2006, 1:45pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/26 "2006-01-19T13:45:28Z")
> [@Blake](#): > > I am glad to see that we have reached agreement. Your argument that an organism isn’t alive if it requires assistance from other organism to reproduce is total nonsense. It’s not assistance. Is a human alive? Of course. When humans reproduce, what makes the human baby? Do humans hand over a sperm and an egg to some other species to make the connection? No. A DVD has to hand over its information and a raw disk to a human to make the connection. What **sleestak** was saying is that obviously humans are alive _despite_ needing assistance to live from other organisms. What makes them alive is that they need only the matter and energy that the human body can assemble to make a new human being. That’s your objective difference. ---
**Author:** ![SentientMeat](https://avatars.discourse-cdn.com/v4/letter/s/43a26b/32.png) [@SentientMeat](https://boards.straightdope.com/u/SentientMeat)\ **Post date:** [January 19, 2006, 2:43pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/27 "2006-01-19T14:43:58Z")
If I may chip in, I’m not sure the difference is all that significant really, **Rift**. In the squishy ‘life’, the matter making up the new copy is dispersed throughout the environment and the “information is impressed onto it” by (effectively) the electrostatic potentials in the DNA molecules _over a long time_ (from conception), via the placenta (‘a delivery system which is discarded after the copy has been formed from the substrate’). In DVD replication, the difference IMO is the _speed_ at which the copy is formed, and the fact that the matter comprising the substrate was not dispersed but all in one place. Again, it is effectively electrostatic potentials which mediate the replication process. (Or if you prefer, since such potentials are caused by regions of different optical reflectivity in the DVD case, it would be a closer analogy to talk about computer files and programs in general as the “life”, which lives in a silicon _environment_ - I’m sure we could tinker with the analogy still further to convince you that the buffer memory, or whatever it is you’re saying a DVD needs to replicate that a human doesn’t, is a somewhat arbitrary distinction to make.) ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [January 19, 2006, 3:03pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/28 "2006-01-19T15:03:21Z")
> [@Plynck](#): > > I am talking about any sort of life, and I believe that most of us would refer to sperm and eggs as alive, even when they are separate. My take on the sperm and ovum (egg cell if you will): The sperm is mobile and active and alive. The ovum OTOH is passive and if viable has the capacity for life if it is NOT ‘dead’ or incapable of being fertilized. The ovum is in some manner alive prior to fertilization. 🙂 ---
**Author:** ![Plynck](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Plynck](https://boards.straightdope.com/u/Plynck)\ **Post date:** [January 19, 2006, 3:34pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/29 "2006-01-19T15:34:32Z")
Although this may already be put to bed, the issue of “assistance” raises the question of symbiotic relationships/diseases which require differing life forms to exist. I don’t think that they can be excluded from the category we define as “life”. I do have a question about one of the definitions advanced by Cecil: > [@](#): > > **Life reverses local entropy.** Popularized by Isaac Asimov. In lay terms, life reverses the default trend toward ever-greater disorganization… In contrast to, say, fire, which in its uncontrolled form is one of your more basic entropic phenomena, life is a creative force. Admittedly that idea isn’t much help in deciding what’s alive and what ain’t. The chemical reactions occurring for the universe’s first few billion years led inexorably to our teeming world, yet no one would describe them as life. But so what? The claim is that there is a powerful antientropic force in the universe (at a certain level of organization, it’s called natural selection), of which we are the latest and coolest manifestation. etc. No one would consider the Internet to be alive, and many think of it as somewhat chaotic. But what of the web crawlers/bots/spiders that are developed to provide organization to this information. Our everyday life on the Web puts us in contact with the products of their work. Commerce will demand more and more intelligence from these entities, and they will continue to adapt to their environment. And they are clearly reversing entropy. Do they fit the definition of life as stated above? > [@spingears](#): > > The ovum is in some manner alive prior to fertilization. 🙂 Schrodinger’s egg? 😃 ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 19, 2006, 10:57pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/30 "2006-01-19T22:57:39Z")
> [@Spatial Rift 47](#): > > It’s not assistance. Is a human alive? Of course. When humans reproduce, what makes the human baby? Do humans hand over a sperm and an egg to some other species to make the connection? No. A DVD has to hand over its information and a raw disk to a human to make the connection. By this definition flowering plants are not alive since they do indeed hand over sperm, in the form of pollen, to some other species to make the connection. Quite clearly trees are alive, yet by your standard handing over the genetic material to another species means that something is not alive. This is clearly nonsense. > [@](#): > > What **sleestak** was saying is that obviously humans are alive _despite_ needing assistance to live from other organisms. What makes them alive is that they need only the matter and energy that the human body can assemble to make a new human being. That’s your objective difference. It is objective, unfortunately it’s also quite clearly nonsense. To accept it at all we also need to accept that plants are not alive, something I am not willing to accept. Plants need the matter and energy of other species, in some cases human beings, before they can assemble new plants. So are you claiming that plants are not alive? ---
**Author:** ![Spatial\_Rift\_47](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Spatial\_Rift\_47](https://boards.straightdope.com/u/Spatial_Rift_47)\ **Post date:** [January 19, 2006, 11:20pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/31 "2006-01-19T23:20:36Z")
Dang, this is _hard_. Obviously plants need to be included in the “alive” category. Although an external object (in a flower’s case, a bee) is what moves the pollen, the bee does not make the pollen, the flower does. Nor does the bee make the cells that recieve the pollen and germinate, the flower makes those too. In the case of the DVD, the DVD didn’t make the information on it, nor did it make the raw disk onto which said information is copied. So, in the interests of clarity, I’m going to state here a revised definition of life. An entity can be said to be alive if it meets the following criteria: 1. It takes in energy. 2. It, all by itself, has the capability to physically assemble the matter and energy needed to produce a copy of itself that preserves information from the original. How’s that? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 19, 2006, 11:55pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/32 "2006-01-19T23:55:41Z")
> [@Spatial Rift 47](#): > > Dang, this is _hard_. Which just proves the old adage, life’s a bitch 😃 > [@](#): > > Although an external object (in a flower’s case, a bee) is what moves the pollen, the bee does not make the pollen, the flower does. Nor does the bee make the cells that recieve the pollen and germinate, the flower makes those too. No, the DVD doesn’t make the physical storage mechanism for its information, but that applies to animals as well. You don’t make the amino acids or nucleic acids or carbohydrates that comprise your body, you simply extract them prefabricated from the environment as they become available. That is not different to a DVD taking a prefabricated disc from the environment as it becomes available. So are animals not alive because they can’t make the raw materials on which their information is copied? > [@](#): > > In the case of the DVD, the DVD didn’t make the information on it, nor did it make the raw disk onto which said information is copied. OK, so let’s produce a DVD with an autoplay function. When inserted in a burner it automatically writes all its information to the hard disk, along with a file that automatically burns a copy when a blank CD is later put in the drive. So now the DVD does make the information on it. > [@](#): > > So, in the interests of clarity, I’m going to state here a revised definition of life. An entity can be said to be alive if it meets the following criteria: > > 1. It takes in energy. > 2. It, all by itself, has the capability to physically assemble the matter and energy needed to produce a copy of itself that preserves information from the original. By this definition no animal or fungus is alive. Animals and fungi are obligate heterotrophs, They are completely unable to assemble, all by themselves, the matter and energy needed to produce a copy of themselves. They need to extract that matter and energy, preconstructed, from other life forms. ---
**Author:** ![Spatial\_Rift\_47](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Spatial\_Rift\_47](https://boards.straightdope.com/u/Spatial_Rift_47)\ **Post date:** [January 20, 2006, 4:07am UTC](https://boards.straightdope.com/t/what-defines-life/340557/33 "2006-01-20T04:07:01Z")
> [@Blake](#): > > No, the DVD doesn’t make the physical storage mechanism for its information, but that applies to animals as well. You don’t make the amino acids or nucleic acids or carbohydrates that comprise your body, you simply extract them prefabricated from the environment as they become available. That is not different to a DVD taking a prefabricated disc from the environment as it becomes available. > > So are animals not alive because they can’t make the raw materials on which their information is copied? > [@Blake](#): > > By this definition no animal or fungus is alive. Animals and fungi are obligate heterotrophs, They are completely unable to assemble, all by themselves, the matter and energy needed to produce a copy of themselves. They need to extract that matter and energy, preconstructed, from other life forms. I’d like to focus only on the reproductive actions. Whatever else the alleged lifeform (henceforth, AL) does is irrelevant to the question at hand, namely whether or not it can reproduce. So sure, a woman takes in vitamins and other helpful compounds when she eats, but what makes it reproduction is that her body assembles those into an egg cell, ready for fertalization, and mate takes in the same and similar compounds and assembles them into a sperm cell ready to fertilize. A DVD does not participate in the actual imprinting of information onto a new, raw disk. > [@Blake](#): > > OK, so let’s produce a DVD with an autoplay function. When inserted in a burner it automatically writes all its information to the hard disk, along with a file that automatically burns a copy when a blank CD is later put in the drive. So now the DVD does make the information on it. The DVD still doesn’t emit a laser that imprints the information onto the new disk, the burner does that. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 20, 2006, 10:42pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/34 "2006-01-20T22:42:44Z")
> [@Spatial Rift 47](#): > > … sure, a woman takes in vitamins and other helpful compounds when she eats, but what makes it reproduction is that her body assembles those into an egg cell, ready for fertalization, and mate takes in the same and similar compounds and assembles them into a sperm cell ready to fertilize. A DVD does not participate in the actual imprinting of information onto a new, raw disk. Of course it participates. It contains the information as well as headers on how that information is to be tranferred etc. And as I pointed out, it is simplicity itself to rig up a DVD that not only participates in but totally controls its own copying. > [@](#): > > The DVD still doesn’t emit a laser that imprints the information onto the new disk, the burner does that. A woman doesn’t emit amino acids that imprint information onto the developing zygote, the food animals do that. You have still failed to provide any objective difference here. Whether we are discussing a human body or a DVD the object at hand is only providing the information to be copied. It needs to be placed into an environment with the prefabricated materials required to copy the information on to. It doesnt matter whether we are talking about reproduction or simply metabolising. The fact is that obligate heterotrophs are incapable of producing the materials they need to reproduce just as a DVD is. They need to be placed into an environment with those necessary materials already prefabricated and available in order to be able to reproduce. That is true in both cases. Similarly obligate heteretrophs are to produce the energy needed to imprint information onto a new cell, whether that cell is a zygote or not. They need to get that energy from a totally different organism. THis is no different at all to a DVD using laser energy from another source. ---
**Author:** ![GreyMatters](https://avatars.discourse-cdn.com/v4/letter/g/a9a28c/32.png) [@GreyMatters](https://boards.straightdope.com/u/GreyMatters)\ **Post date:** [January 20, 2006, 10:52pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/35 "2006-01-20T22:52:55Z")
> [@Blake](#): > > I fail to see the difference between ‘copying the information on a DVD into a new physical medium’ and ‘creating a new DVD’. Can you explain what the difference is? When I burn a DVD and give it to a friend, haven’t I created a new DVD? It seems I must have done since I still posses the original. > > I realy don’t see the distinction. When my dog has pups it doesn’t create a duplicate of itself using the same matter. It utilises new matter to create a facsimile. How does this differ from me copying a DVD? In both cases I had one version of something, then I took new matter form another source and onverted that into two verison witht he same approximate information. > > I’m really puzzled what you see as being the distinction. Well, DVD’s can not, possibly, copy themselves. By themselves, DVDs sit in one place and exist, doing nothing, forever and ever and ever until something ALIVE comes along and exacts the copying process on that DVD, which to you seems like a process that a lifeform executes. DVDs are not alive and neither are memes or the written word. The arguments that these are alive are just plain wrong. Sorry buddy. ---
**Author:** ![Hoodoo\_Ulove](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hoodoo\_Ulove](https://boards.straightdope.com/u/Hoodoo_Ulove)\ **Post date:** [January 20, 2006, 10:54pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/36 "2006-01-20T22:54:34Z")
> [@Blake](#): > > It also includes memes, the written word, DVDs and computer algorithms as being alive, amongst other things… That is obviously problematic since none of those things are alive. **Blake** , you’ve quite cogently been pointing out that the definitions of life on offer do not exclude memes, DVDs and such and yet you say they _aren’t_ alive. Why? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 20, 2006, 11:48pm UTC](https://boards.straightdope.com/t/what-defines-life/340557/37 "2006-01-20T23:48:09Z")
> [@GreyMatters](#): > > Well, DVD’s can not, possibly, copy themselves. By themselves, DVDs sit in one place and exist, doing nothing, forever and ever and ever until something ALIVE comes along and exacts the copying process on that DVD, which to you seems like a process that a lifeform executes. A computer with a burner is what “exacts the copying process on that DVD”. Are you saying that a computer is something ALIVE? Or are you simply rehashing the old ground about using the energy of another organism for transport, in which case you are arguing that a pollen grain is not alive. By themselves, pollen grains sit in one place and exist, doing nothing, forever and ever and ever until something ALIVE comes along and exacts the copying process on that pollen grain. So are you trying to argue that pollen grain is not alive? > [@](#): > > DVDs are not alive and neither are memes or the written word. The arguments that these are alive are just plain wrong. Sorry buddy. Now there’s an eloquent argument. It’s worng coz it’s wrong. :rolleyes: Thank you for that valuable contribution. > [@Hoodoo Ulove](#): > > Blake, you’ve quite cogently been pointing out that the definitions of life on offer do not exclude memes, DVDs and such and yet you say they aren’t alive. Why? Quite simply because when people talk about living things they do not intend to include books or stone tablets. Poeple instinctively know what a living thing is, and while it may not be perfect it certainly does not include chunks of stone. You are quite free to say that a 12 tonne stone block is alive if you wish to, but I doubt anyone else will understand you. ---
**Author:** ![GreyMatters](https://avatars.discourse-cdn.com/v4/letter/g/a9a28c/32.png) [@GreyMatters](https://boards.straightdope.com/u/GreyMatters)\ **Post date:** [January 21, 2006, 12:29am UTC](https://boards.straightdope.com/t/what-defines-life/340557/38 "2006-01-21T00:29:01Z")
> [@Blake](#): > > A computer with a burner is what “exacts the copying process on that DVD”. Are you saying that a computer is something ALIVE? > > Or are you simply rehashing the old ground about using the energy of another organism for transport, in which case you are arguing that a pollen grain is not alive. By themselves, pollen grains sit in one place and exist, doing nothing, forever and ever and ever until something ALIVE comes along and exacts the copying process on that pollen grain. So are you trying to argue that pollen grain is not alive? > > Now there’s an eloquent argument. It’s worng coz it’s wrong. :rolleyes: > > Thank you for that valuable contribution. > > Quite simply because when people talk about living things they do not intend to include books or stone tablets. Poeple instinctively know what a living thing is, and while it may not be perfect it certainly does not include chunks of stone. > > You are quite free to say that a 12 tonne stone block is alive if you wish to, but I doubt anyone else will understand you. Lets use Wikipedia for a source on a definition of life, to start, then shall we?: Organization - Living things are comprised of one or more cells, which are the basic units of life. Metabolism - Metabolism produces energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life. Growth - Growth results from a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter. Adaptation - Adaption is the accommodation of a living organism to its environment. It is fundamental to the process of evolution and is determined by the individual’s heredity. Response to stimuli - A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. Plants also respond to stimuli, but usually in ways very different from animals. A response is often expressed by motion: the leaves of a plant turning toward the sun or an animal chasing its prey. Reproduction - The division of one cell to form two new cells is reproduction. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth. [cite](http://en.wikipedia.org/wiki/Life) From that cite, DVDs, memes or the written word fail to pass the catagories of: Organization, Metabolism, Growth, Adaptation, Response to stimuli and Reproduction. Wow, they don’t seem to pass ANY of the tests. Wierd how an inanimate object can’t seem to pass the qualifications to be considered a lifeform. Now, I am all for the possibility that there is life that is completely different than that described in the cite. But, if you want to argue that such life exists then it is up to you to prove it. It is not up to us to stretch our definitions passed the breaking point to accomodate your falacious premises. You need to show how our definitions are wrong and prove it. Saying that the replication process of both a lifeform and an inanimate object can be thought of in similar metaphors is proof that DVDs are alive just won’t cut it. Also, I did not say your arguments are wrong because they are wrong. I just said they are wrong. Ridiculously wrong. Note: I have seen you do not claim DVDs are alive and are just playing devil’s advocate. For that, I give you the star of the day. I like the devil’s advocate. ---
**Author:** ![Spatial\_Rift\_47](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Spatial\_Rift\_47](https://boards.straightdope.com/u/Spatial_Rift_47)\ **Post date:** [January 21, 2006, 5:25am UTC](https://boards.straightdope.com/t/what-defines-life/340557/39 "2006-01-21T05:25:15Z")
**Blake** , could you give me some indication of what you’re looking for with an objective difference? It seems I’m not providing what you’re looking for. And I think it does matter whether we discuss metabolization or reproduction, since the definition I’ve been attempting to clarify: > [@Spatial Rift 47](#): > > … it has to take in energy (in some form, doesn’t matter how), and reproduce. is about taking in energy and reproducing. The entire argument thus far, as far as I’ve understood it, is about how to precisely define “reproduction” so that it includes things we all agree should be considered “alive” and excludes things like DVDs and computer memes and such. Whatever else an alleged lifeform does is irrelevant to the question of whether it can reproduce. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [January 21, 2006, 8:24am UTC](https://boards.straightdope.com/t/what-defines-life/340557/40 "2006-01-21T08:24:07Z")
> [@GreyMatters](#): > > From that cite, DVDs, memes or the written word fail to pass the catagories of: Organization, Metabolism, Growth, Adaptation, Response to stimuli and Reproduction. > > Wow, they don’t seem to pass ANY of the tests. Wierd how an inanimate object can’t seem to pass the qualifications to be considered a lifeform. You do realise of course that you are arguing a complete strawman. We are discussing, and have been discussing, why a defintintion given on the firts page of this thread fails entirely because it can not preclude a DVD or a book. All you have done is introduced a completely separate definition of life which hinges entirely on cellularity. It’s totally irrelvant to the discussion. > [@](#): > > Saying that the replication process of both a lifeform and an inanimate object can be thought of in similar metaphors is proof that DVDs are alive just won’t cut it. Once again, it won’t cut it because it won;t cut it. Such pithy argument. :rolleyes: > [@](#): > > Also, I did not say your arguments are wrong because they are wrong. I just said they are wrong. Ridiculously wrong. Yes, they are wrong, not for any reason but simply because you say they are worng. Man, I wish we had you on our team during the national debating finals at uni. Now how about injecting somehting of substance and relevance into the debate? Give me an objective reason why DVDs are not alive based on the defintion given? You seem to be a bit slow on this one. Nobody has suggested that we can’t simply define life as “cells” which is all that the Wikipedia defintion does. We could also define it as “DNA”. But that doesn’t aid this discussion one bit because of course it will mean that any extraterrestrial life willhave to be deemed non-living. > [@Spatial Rift 47](#): > > Blake, could you give me some indication of what you’re looking for with an objective difference? It seems I’m not providing what you’re looking for. By objective difference I mean simply a difference that we can quantify. Something that isn’t entirely based on your or my subjective interpretation of what constitutes ‘something’. For example ‘needing energy’ isn’t an objetcive difference because a laser is neither more nor less aneegry than sunlight. Similary ‘requiring building materials’ isn’t objective because amino acids are materials just the same as a blank DVD is. We need something that we can look at and say yes, the DVD doesn’t have that trait. Then we can start to discuss whether the difference is meaningful or simply an arbitrary line in the sand. It’s easy enough to objetcively exclude DVDs by saying that life doesn;t requires laser energy, but the question then becomes why you made that decision. > [@](#): > > And I think it does matter whether we discuss metabolization or reproduction… You have misinterpreted me. I am not saying that disussion of reproduction is irrlevant, I am saying that reproduction in this instance isn’t objectively different from metabolism. Just as metabolism for heterotrophs requires pre-fabricated complex materials so does reproduction. There’s no difference that we can quantify between the need for materials for reproduction and the need for materials for metabolism. IOW when it comes to a requirement for prefabricated complex materials it doesn’t matter if we discuss metabolism or reproduction. The requirements are excatly the same. By all means attempt to separate out life based on reproduction, but when reproduction and metabolism both require complex prefabricated materials in heterotrophs you can not use the requirement for complex prefabricated materials as a criterion for non-life. [Previous page](https://boards.straightdope.com/t/what-defines-life/340557.md?page=1) [Next page](https://boards.straightdope.com/t/what-defines-life/340557.md?page=3)