Thread: proposed deffinition for life

now this is rather ambitious for me to attempt however i think that our(the human race's) beating around the bush on a clear deffinition of what is life and what is not life needs to end soon.

the definition i propose is that a living organism is an aqueous solution with the property of selectively exchanging solvent and solutes with its environment, chemically reacting with ingested chemicals, decreasing the entropy within its borders, and creating aqueous solutions with similar properties.

if i'm missing anything that's generally considered an aspect of all living things then please state so.

one will notice that many viruses do not meet my definition of life as many are not themselves aqueous solutions, but are only found in them. however some viruses enclosed in envelopes derived from the host cell might be considered living under this definition, depending on their properties.

I am largely in disagreement with everything you have written. Some specific points:
1. the human race has not been beating around the bush about a definition of life: the bulk of the human race either have a practical folk definition or couldn't give a damn.
2. Those who have a scientific interest in the definition of life have not been backward in coming forward. At an exobiology conference about six years ago the participants came up with over eighty definitions.
3. Your definition is the least adequate of any I have seen.
4. Until we have life that evolved with a different common ancestor we are comparing an apple with nothing: pointless exercise.

Dissolve me in a solvent please.

ok. Wheres the acid?

Maybe a more interesting way to come at the issue is from complexity theory.

The notion of self-organizing complex systems in nature continues to gain traction among scientists. Sometimes called dissipative systems (I think this term came from Ilya Prigogine), self-organizing complex systems are defined generally to include, but not be limited to, biological organisms.

So, it begs the question: When is a self-organizing complex system alive and when isn't it?

Complexity theorists, where are you on this?

Originally Posted by starlarvae

Complexity theorists, where are you on this?

That's not a simple question.

Quite complex

Originally Posted by starlarvae

The notion of self-organizing complex systems in nature continues to gain traction among scientists. Sometimes called dissipative systems (I think this term came from Ilya Prigogine), self-organizing complex systems are defined generally to include, but not be limited to, biological organisms.

Originally Posted by saul

the definition i propose is that a living organism is an aqueous solution with the property of (...) decreasing the entropy within its borders

decreasing the entropy within a system is a synonym for increasing the complexity/organization of the system. so i define life with the requirement of complexity however that is by no means the extent of my requirements.

Originally Posted by Ophiolite

Until we have life that evolved with a different common ancestor we are comparing an apple with nothing: pointless exercise.

and untill we know the difference between apples and oranges we could be comparing our apple to a rock and think it's the same thing. we need a clear definition of life before we encounter exobiology or else we won't know if what we're looking at is life, unless of course it resembles our own biology with very few differences(a disappointing possibility, in my eyes).

Dissolve me in a solvent please.

Ha ha

Originally Posted by saul

we need a clear definition of life before we encounter exobiology or else we won't know if what we're looking at is life, unless of course it resembles our own biology with very few differences(a disappointing possibility, in my eyes).

No we don't, because a clear and meaningful definition is currently not possible. We need what we already have: a diverse range of definitions of varying degrees of inclusivity and exclusivity. That minimises the risk of missing out on exotic life forms when we encounter them and provides a rich resource as a foundation for developing life detection methods.

We do not currently need a definition that encompasses exotic life forms. By which I assume most people are thinking of exobiology.

If and when humanity encounters an exotic life form, under the ice at Europa or wherever, then we can reform our definitions. Until then, the whole damn exercise is totally pointless. A definition that encompasses Earth life is 100% sufficient until something else is found.

skeptic i agree that currently our definition of life cannot be custom fit to encompass "exotic life" as we do not know what form that life will come in.

however, some definition of earth life must still exist. the reason i believe it is important is because of pseudo-life forms such as viruses composed entirely of proteins and nucleic acids. these pseudo-life are the subject of much debate as to whether or not they are alive (http://serc.carleton.edu/microbelife...viruslive.html) and without our knowing what it is that constitutes life, these debates can not reach a conclusion.

additionally, if we are unable to determine whether or not a collective of organic molecules such as a virus is alive, what hope have we of identifying truely exotic life forms when we encounter them?

Originally Posted by saul

without our knowing what it is that constitutes life, these debates can not reach a conclusion.

Small problem there.
Biologists who try to come up with definitions of life just modify the wording to include or exclude viruses according to their prejudices.

The best definition of life I saw goes something like ...

"Life is a complex system of organic molecules which undergo both reproduction and evolution."

The biologist who wrote this used the word 'complex' deliberately to exclude viruses. I think, myself, that the definition would be better without the word 'complex', and include viruses. But that is just my opinion.

Originally Posted by saul

however, some definition of earth life must still exist. the reason i believe it is important is because of pseudo-life forms such as viruses composed entirely of proteins and nucleic acids. these pseudo-life are the subject of much debate as to whether or not they are alive (http://serc.carleton.edu/microbelife...viruslive.html) and without our knowing what it is that constitutes life, these debates can not reach a conclusion.

Humans have a great weakness and a great strength. Their great strength is their ability to perceive patterns and create classification systems. Their great weakness is their ability to perceive patterns and create classification systems.

Life versus non-life is a false dichotomy. There is a spectrum of increasing complexity and where we put the dividing line on that spectrum is wholly arbitrary and, to my mind, pretty damn irrelevant. If we get hung up on trying to place it we fail to see the continuity that exists.

Originally Posted by Ophiolite

Originally Posted by saul

however, some definition of earth life must still exist. the reason i believe it is important is because of pseudo-life forms such as viruses composed entirely of proteins and nucleic acids. these pseudo-life are the subject of much debate as to whether or not they are alive (http://serc.carleton.edu/microbelife...viruslive.html) and without our knowing what it is that constitutes life, these debates can not reach a conclusion.

Humans have a great weakness and a great strength. Their great strength is their ability to perceive patterns and create classification systems. Their great weakness is their ability to perceive patterns and create classification systems.

Life versus non-life is a false dichotomy. There is a spectrum of increasing complexity and where we put the dividing line on that spectrum is wholly arbitrary and, to my mind, pretty damn irrelevant. If we get hung up on trying to place it we fail to see the continuity that exists.

This, basically, is all there really is to be said on the matter.

We can draw boundaries around things for convenience or as a shorthand, but we have to be so very careful about thinking they mean more than they really do.