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"…we really do not have a good working definition of what constitutes life. At the most fundamental level, we still do not know whether the difference between a

by Radim 9y ago

"…we really do not have a good working definition of what constitutes life. At the most fundamental level, we still do not know whether the difference between animate and inanimate is simply a difference in kind or degree." What would a "difference in kind" look like? I thought it was pretty well established at this point there's no magic, that "life" is just another layer in the layers of natural complexity, how matter organizes itself, from physics to chemistry to biology to sociology and ecology. Why would there be an expectation of a sharp (non-linguistic) boundary between "life" and "non-life", animate and inanimate, physics and chemistry, chemistry and biology?

jessriedel 9y ago
There are sharp phase transitions between different phases of matter. It's a difference in kind, but it's all made out of atoms.
- eesmith 9y ago
  Except when there isn't. https://en.wikipedia.org/wiki/Critical_point_(thermodynamics) https://en.wikipedia.org/wiki/Critical_point_(thermodynamics... > "Above the critical point there exists a state of matter that is continuously connected with (can be transformed without phase transition into) both the liquid and the gaseous state. It is called supercritical fluid."
  - jessriedel 9y ago
    I'm well aware of this and it doesn't change my point.
    - eesmith 9y ago
      Which is that we should expect a sharp transition between life and not-life because there are sharp transitions between some phases? I don't see how that fits. Even if you think of "life" as a phase transition, why does it have to be a sharp transition?
      - jessriedel 9y ago
        It doesn't have to be. I'm just rebutting Radim's suggestion that since living things and non-living things are both made out of atoms we should expect that the difference between living and non-living is only of degree rather than kind.
        eesmith 9y ago
        The phrase was "Why would there be an expectation of a sharp ..." I agree - why would we expect a sharp transition? When a radioactive particle decays, it too is a sharp transition. (By which I mean the time scale is very short. At sufficiently fine resolution, it's hard to tell exactly when an atom of element X becomes something other than an atom of element X.) That there are examples of very fast transformation doesn't mean that Radim is incorrect in asking why we would expect the difference between life and non-life to be one of those sharp transitions. In a tabula rasa sense, it might be a good cautionary reminder to consider exceptions like what you pointed out. But it's "pretty well established" (to quote Radim) that the boundary between life and non-life is not distinct. The standard question is, are viruses alive? The usual answer is "no", but https://en.wikipedia.org/wiki/Mimivirus#Implications_for_defining_%22life%22 https://en.wikipedia.org/wiki/Mimivirus#Implications_for_def... pushes it close to yes. Humans have created an organism with a synthetic genome. Give another decade or two and biologists will be creating semi-alive forms to explore what the boundary means. Further, there are definitions beyond the strictly biological one: https://en.wikipedia.org/wiki/Life#Definitions https://en.wikipedia.org/wiki/Life#Definitions .
        jessriedel 9y ago
        > it might be a good cautionary reminder to consider exceptions like what you pointed out. It's not just a single exception, it's a huge class of counterexamples which is the focus of study for much of the field of condensed matter physics.
        eesmith 9y ago
        And there is an much larger class of examples.
    - Radim 9y ago
      And it is a good point. Perhaps what they meant by that "difference in kind vs degree" was just such a (hypothesized) phase transition. The frantic scramblings that happen around phase transitions are often fascinating [0] and worth awarding an explicit name on either side, however fuzzy the inflection point. Fair enough. [0] https://www.quantamagazine.org/beyond-the-bell-curve-a-new-universal-law-20141015/ https://www.quantamagazine.org/beyond-the-bell-curve-a-new-u...

by Radim 9y ago

jessriedel 9y ago

There are sharp phase transitions between different phases of matter. It's a difference in kind, but it's all made out of atoms.

eesmith 9y ago
Except when there isn't. https://en.wikipedia.org/wiki/Critical_point_(thermodynamics) https://en.wikipedia.org/wiki/Critical_point_(thermodynamics... > "Above the critical point there exists a state of matter that is continuously connected with (can be transformed without phase transition into) both the liquid and the gaseous state. It is called supercritical fluid."
- jessriedel 9y ago
  I'm well aware of this and it doesn't change my point.
  - eesmith 9y ago
    Which is that we should expect a sharp transition between life and not-life because there are sharp transitions between some phases? I don't see how that fits. Even if you think of "life" as a phase transition, why does it have to be a sharp transition?
    - jessriedel 9y ago
      It doesn't have to be. I'm just rebutting Radim's suggestion that since living things and non-living things are both made out of atoms we should expect that the difference between living and non-living is only of degree rather than kind.
      - eesmith 9y ago
        The phrase was "Why would there be an expectation of a sharp ..." I agree - why would we expect a sharp transition? When a radioactive particle decays, it too is a sharp transition. (By which I mean the time scale is very short. At sufficiently fine resolution, it's hard to tell exactly when an atom of element X becomes something other than an atom of element X.) That there are examples of very fast transformation doesn't mean that Radim is incorrect in asking why we would expect the difference between life and non-life to be one of those sharp transitions. In a tabula rasa sense, it might be a good cautionary reminder to consider exceptions like what you pointed out. But it's "pretty well established" (to quote Radim) that the boundary between life and non-life is not distinct. The standard question is, are viruses alive? The usual answer is "no", but https://en.wikipedia.org/wiki/Mimivirus#Implications_for_defining_%22life%22 https://en.wikipedia.org/wiki/Mimivirus#Implications_for_def... pushes it close to yes. Humans have created an organism with a synthetic genome. Give another decade or two and biologists will be creating semi-alive forms to explore what the boundary means. Further, there are definitions beyond the strictly biological one: https://en.wikipedia.org/wiki/Life#Definitions https://en.wikipedia.org/wiki/Life#Definitions .
        jessriedel 9y ago
        > it might be a good cautionary reminder to consider exceptions like what you pointed out. It's not just a single exception, it's a huge class of counterexamples which is the focus of study for much of the field of condensed matter physics.
        eesmith 9y ago
        And there is an much larger class of examples.
  - Radim 9y ago
    And it is a good point. Perhaps what they meant by that "difference in kind vs degree" was just such a (hypothesized) phase transition. The frantic scramblings that happen around phase transitions are often fascinating [0] and worth awarding an explicit name on either side, however fuzzy the inflection point. Fair enough. [0] https://www.quantamagazine.org/beyond-the-bell-curve-a-new-universal-law-20141015/ https://www.quantamagazine.org/beyond-the-bell-curve-a-new-u...