Can a robot be called as Living thing?

  1. Can a self replicating, or self growing robot (programmed to make logical decisions) can be called as Living thing?

    If not, what is the definition of living thing?
  2. jcsd
  3. It depends upon one's definition of living thing. I think that most folks would insist that the creature be biological rather than mechanical in nature in order to be "living."

    But in the far flung future, it may be possible for science to create biologically-based creatures to serve us. Then we may be asking if they could be considered as "robots."

  4. In biological life, energy and informations are stored in matter made up of mainly C, N, H etc (Evolution has chosen those atoms) where as in robot, there are stored in inorganic materials. So both does the same job in different platform. It is possible to restart a robot which has stopped working due to the lack of energy by giving energy as input.
    Is it possible, at least theoretically, to make a dead man alive using the same principle..
    Last edited: Dec 8, 2010
  5. DaveC426913

    DaveC426913 16,539
    Gold Member

    The basis of the definition of life is:
    - it eats and excretes
    - respirates
    - grows
    - reproduces
    - reacts to stimuli

    There's all sorts of nuancing but it starts with those.
  6. It seems easy enough to imagine the building of a machine that can do all those things. I have a feeling that the term "living" is too vague, as it would permit endless quibbling. Perhaps we can even speculate that "living" is a fundamentally meaningless term, or at least should find a home under the philosophy place.
  7. DaveC426913

    DaveC426913 16,539
    Gold Member

    A machine that could reproduce itself would not be easy.

    What makes you think life is so complex?
  8. Here's a sort of thought experiment:
    If a person has a prosthetic leg, is he still human? Of course!
    What if he has two prosthetic legs?
    Two prosthetic legs and an artificial heart?
    What if every organ is replaced with a mechanical substitute, even the brain, the contents of which are "downloaded" into a network with transistors instead of neurons?

    After which gradual step is he suddenly no longer human?
  9. Maybe not easy, or even very practical, but it seems obvious that it could be done.

    I didn't say it was complex. My point was that the definition of "living" is complex.

  10. Danger

    Danger 9,663
    Gold Member

    I disagree that it must eat and excrete, only because that the human concepts of those functions are personalised. They might not be recognised in a normal manner, but are unmissable by those who grew up with the crap.
  11. Born2bwire

    Born2bwire 1,776
    Science Advisor
    Gold Member

    Maybe, but I think that some form of consumption is required in order to reproduce oneself. Otherwise, you continually strip yourself of resources. In that manner, I would think of consumption as being able to take in readily available resources and manipulate them to suit your needs. Whether it is our eating and digestion of foodstuffs to provide us with energy and matter or a robot taking in scrap metal or ore to smelt into materials to build the frame of a new robot.

    In this manner, sure we can construct robots that are self-assembling, but they are unable to build the parts themselves.
  12. Danger

    Danger 9,663
    Gold Member

    I agree, Born. I just felt like playing Devil's Advocate in order to point out that neither intake nor exhaust will necessarily be recognizable by our species. Really, I've taken a crap or two that would never be recognized as having come from a human...
  13. DaveC426913

    DaveC426913 16,539
    Gold Member

    We were discussing life versus non-life. Human versus non-human is a very different question.

    The central paradox here is often known as the Theseus' Ship Paradox.

    If Theseus replaces every wooden plank on his ship one by one, is it still the same ship?
    Last edited: Dec 9, 2010
  14. One of the unstated assumptions of my argument was that the human is also alive after each gradual step. You could redo the questions, this time asking "After which gradual step is he suddenly not alive?"

    Of course, that would be a very complicated robot. A more pertinent question would be "What is the simplest robot that could be described as alive?"

    But before I go there, do we all agree that a sufficiently complicated machine could be called "alive"?
  15. K^2

    K^2 2,470
    Science Advisor

    I would only disagree with DaveC's criteria on eating/excreting and respiration. By that definition, anaerobic bacteria are not alive, since they require no respiration. Response to stimuli is also questionable, but only because of vagueness.

    I would start with reproduction as most important criterion. It must self-reproduce however. I would not classify something like a virus as alive. Otherwise, we must include all existing technology in the definition.

    I would then replace all statements about feeding/breathing or whatever into the single most broad definition. It must consume energy to maintain it's own Gibbs' free energy at above equilibrium level. This is all we really need to exclude "simple reproduction" of things like growing crystal.

    Anything that follows these two criteria will evolve with changing environment. If it doesn't end up evolving to respond to stimuli or to do any of the other things we associate with living things, then it obviously doesn't need them.

    Basically, as long as these two criteria are fulfilled, I'd call it alive regardless of origin.
  16. DaveC426913

    DaveC426913 16,539
    Gold Member

    Yes. Eating and excreting are terms we put a lot of meaning on. Ultimately, it must consume raw materials and emit waste materials. Eating/excreting and respiration are both subsumed under that.

    If it responds to no external stimuli, is it alive at all?

    Even that has its vagueness. There are organisms that can't reproduce without the help of other organisms (some parasites and symbiotes). Is that kind of like saying a machine needs the symbiotic help of another machine to produce its raw materials?

    And it must grow.
  17. Danger

    Danger 9,663
    Gold Member

    I find myself in the peculiar position of both agreeing and disagreeing with someone.
    I consider a virus to be alive. My best argument in favour of that is the fact that inoculations are specified to contain a killed virus.
  18. I think "having the free energy above equilibrium level" is the most basic condition. Rest of all the conditions, like growth, reproduction, consciousness etc are the properties gained in the process of evolution, depending upon at what stage of evolution it has reached. May be a growing crystal can evolve to a stage where it can do all the function what now we consider as the characteristics of living thing.
  19. K^2

    K^2 2,470
    Science Advisor

    If I remove support from under a rock, it drops. And many living organisms can't respond to more than a pressure change. So it's way too vague.

    I agree. This needs work. What I'm trying to get to is difference between requiring a host for environment, in case of a parasite, and needing host to do the actual reconstruction, in case of a virus. Former should be classified as alive, while later should not. Any thoughts on how to formulate it better?

    Reproduction sort of forces growth at some stage. If it never grows past that point, I see no reason to disqualify it from being alive.
    But if it doesn't reproduce, how can it evolve?
  20. Danger

    Danger 9,663
    Gold Member

    You make a good point, Scienceisbest. There has been a lot of speculation by reputable scientists as to whether or not a silicon-based life form is possible, since its valence shell is equal to that of carbon. I like the idea of the possibility, but have no evidence to support it.
  21. DaveC426913

    DaveC426913 16,539
    Gold Member

    Except that a growing crystal is not alive. So we know that definition is too loose.

    Let's also be wary of this word 'evolve'. You are using it simply in the transformative sense (white can evolve into black), but that is not the same as replication with adaptation.
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