Why Call it "Alive"? Exploring Life's Definition

  • Thread starter Mentat
  • Start date
In summary: life has no definable characteristics, we can only come up with a working definition that excludes those things that are clearly not living, while including those things that may be living but we do not have a good enough understanding of to say for sure.

Which choice do you prefer?

  • Forget the whole living/non-living distinction; it's useless.

    Votes: 8 38.1%
  • Devise a working definition for "alive"; it is an important distinction.

    Votes: 6 28.6%
  • Use one of the definitions that already exist, and accept the consequences.

    Votes: 3 14.3%
  • other...

    Votes: 4 19.0%

  • Total voters
    21
  • #1
Mentat
3,960
3
Why call it "alive"?

It has been mentioned innumerable times in previous threads that "life" has no working definition. Most of the definitions that people have tried to devise have either excluded some things that are still considered living, or have included some things that are certainly not considered living.

So, my question is, why did we ever come up with this distinction in the first place? Is it part of our evolutionary (cultural or organic) heritage? What use does it really serve in the long run?

As it is, I see us as having three choices:

1) Abandon the whole "living/non-living" distinction altogether, and move on.

2) Form a fully functioning definition, that allows only those things which we would all agree are "alive" and excludes those things which are obviously "non-living".

3) Use one of the definitions (sets of criteria) that we have already devised and accept the consequence that either some of the things that we thought were "alive" are not, or that some of the things that we've assumed to be definitely "non-living" are indeed alive.

Please give reasons for which you vote for. Along with such reasons, any comments, corrections, or questions that remain on-topic are appreciated :smile:.


Oh, btw, if you think you've got another alternative, then just choose "other..." and then post your alternative (this should seem self-explanatory, but there've been problems in the past, so I figured I'd make sure).
 
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  • #2
I think it important that science comes up with a working definition of what life, being alive, is because accurately defining it would lead to better understanding it and help in its study. Not just for knowledge's sake but for all of lifes sake. Who knows it may lead to saving lives.
 
  • #3
Originally posted by Royce
I think it important that science comes up with a working definition of what life, being alive, is because accurately defining it would lead to better understanding it and help in its study. Not just for knowledge's sake but for all of lifes sake. Who knows it may lead to saving lives.

I ask you, though, how can one say that life even exists, if it has not working definition? IOW, how can it be important to "life" for there to be a definition of it, when its lack of definition makes it seem as though it doesn't exist at all?

I may playing DA here, but I kind of do really want an answer to this, personally.
 
  • #4
The same way that we can say that matter and energy exist without knowing what is is or being able to define it by other than it's properties just as we attempt to define life. Does a photon exist?
 
  • #5
"Alive" and "life" are not special. There are many words that have this property. My wife and I argue about whether something is blue or not. Most words have their black and white zones, and grey areas.

The reason why we argue is not because the concept is nebulous, but because it is important. No matter what definitions you make, because of the importance of the issues, some people will see different things as falling into different catagories. You can draw up your new definitions with the greatest of care, but you are defining your concepts with words. These words will have subtly different meanings to every person. These differences blur the distinctions you think you so carefully made.

Njorl
 
  • #6
Is there a distinct difference between something that is alive, and something that is conscious? Should there be? Would a machine that has the ability to reproduce be considered alive? If not, then why would we be considered alive?

I don't think there can be an accurate discription of what is alive, because of the above questions.
 
  • #7
The more I look at this subject and the more I read into AI and philosophy of the mind, the more any word like "living" looses all meaning. What is important is the consequences. Why? We will never be able to tell if something is 'alive' or if it is faking, the same way as we will never be able to tell if a computer is 'conscious' of if it too is just faking (of course faking implies that it is doing it deliberately, and therefore it is both alive and conscious, but hence is the nature of language, deal with it)

If we attribute meaning to things in terms of its consequences then all of this becomes irrelevant. It acts like life, treat it like it is. Definition will never help us here, as we are bound to rope in a lot of false rejections and false positives, and that’s just not something that you should do to anything that’s 'life'. Just treat it like it is.

As for life and consciousness, well, if 'life' is simply a matter of complexity, then maybe consciousness is a complexity that arises from life. They can be treated the same way, but it’s not necessary that the presence of life imply consciousness.
 
  • #8
Whose work?

There doesn't need to be just one definition, just as there's not one definition of 'force', 'energy', 'action', etc; there are good working definitions used by the folk who need them, in different fields (there's another) of endeavour.

So, it's maybe more important to ask 'who needs the working definition, and for what purposes' than to get hung up on any particular one, let alone try to find a universal one for all of science.

My own interest is ET(L), and a useful definition would include stuff like persistent and repeated deviations from thermodynamic equilibrium, chemical equilibrium; something about organisation, hierarchy, patterns; and more (e.g. reproduction in some sense).
 
  • #9
Originally posted by Royce
The same way that we can say that matter and energy exist without knowing what is is or being able to define it by other than it's properties just as we attempt to define life. Does a photon exist?

There's a difference. Postulating the photon helps us further our knowledge of what we know to be occurring at the subatomic level. What does postulating a distinction between "alive" and "non-living" help?
 
  • #10
Originally posted by revesz
Is there a distinct difference between something that is alive, and something that is conscious?

Yes. Until we devise a working definition, it doesn't mean anything to be "alive", but it does mean something to be conscious.

Would a machine that has the ability to reproduce be considered alive? If not, then why would we be considered alive?

Well, actually, we are machines with the ability to reproduce.
 
  • #11


Originally posted by Nereid
There doesn't need to be just one definition, just as there's not one definition of 'force', 'energy', 'action', etc; there are good working definitions used by the folk who need them, in different fields (there's another) of endeavour.

So, it's maybe more important to ask 'who needs the working definition, and for what purposes' than to get hung up on any particular one, let alone try to find a universal one for all of science.

Interesting, but, how can we know that anything is "alive", if there is no known distinction between "living" things and "non-living" things.

My own interest is ET(L), and a useful definition would include stuff like persistent and repeated deviations from thermodynamic equilibrium, chemical equilibrium; something about organisation, hierarchy, patterns; and more (e.g. reproduction in some sense).

ET(L)? "Evolution theory (Law)"?

Anyway, don't all of those things that you mentioned apply to a virus? And yet, viruses are not considered "alive". Does this mean that option #3 is the best choice, and we must simply accept that some things are alive by definition, even if we don't think they are?
 
  • #12
Mentat, responding to Nereid on multiple definitions: Interesting, but, how can we know that anything is "alive", if there is no known distinction between "living" things and "non-living" things.
It's not so much knowing whether 'something' is "alive", rather that the same 'thing' may be 'alive' according to the working definitions of one field; 'not alive' in another field; 'not within the field of study' of a third field; and 'not a relevant label' according to the working definitions in yet a fourth field. I'm certainly no biologist, but it may be that, to virologists, the distinction between 'living' and 'non-living' is not relevant (indeed, it may even be quite a red-herring), and that 'viable' and 'non-viable' are more important. Perhaps to those who study spores, pollen, deep-freeze, etc a different set of distinctions are used; again, 'living' and 'non-living' may actually be confusing, even misleading.

ET(L) = extra-terrestrial life. As none has been found yet (UFO buffs notwithstanding), working definitions need to be kept in a constant state of review. Personally, it's as exciting to look for evidence of ETL-past (fossil bacteria in rocks in the outflow channels on Mars?) as ETL-present. In the former, a working definition will focus on characteristics and markers for now-extinct life, rather than currently observed reproduction (for example).
 
  • #13
Originally posted by Nereid
It's not so much knowing whether 'something' is "alive", rather that the same 'thing' may be 'alive' according to the working definitions of one field; 'not alive' in another field; 'not within the field of study' of a third field; and 'not a relevant label' according to the working definitions in yet a fourth field. I'm certainly no biologist, but it may be that, to virologists, the distinction between 'living' and 'non-living' is not relevant (indeed, it may even be quite a red-herring), and that 'viable' and 'non-viable' are more important. Perhaps to those who study spores, pollen, deep-freeze, etc a different set of distinctions are used; again, 'living' and 'non-living' may actually be confusing, even misleading.


Very good point, Nereid. Well, I guess, since this is in the Philosophy Forum, my question has more to do with people's personal opinions of whether they can consider something "alive" when there is no working definition for "life". As it is, I can see why professionals in different fields can work with this concept differently.
 
  • #14
That aside, is a neuron alive? It might be in the scientific sense, but we know it isn't quite aware of its existence and the reason behind it. In that case what is that criteria by which we claim to be alive? Certainly no one would use the term "alive" on a robot as we would on a living human being. Is consciousness the distinguishing criteria? How is it that we should cross the demarcating line from being just a massive functional blob of neurons, muscles, skeleton, and whatnots and land in some place completely different from where we start off from? Why would the synchronised actions of neurons somehow give rise to consciousness when we couldn't say the same for a single neuron? (Surely a neuron couldn't feel.)
 
  • #15
Mentat wrote (extracts): ... since this is in the Philosophy Forum, my question has more to do with people's personal opinions of whether they can consider something "alive" when there is no working definition for "life".
Who was it that said they were perfectly capable of thinking 25 contradictory things, even before breakfast (or something similar)?

I really like the idea of exploring what people's opinions on this subject are, in all its undoubtedly riotous and rich diversity!
 
  • #16


How do I know that I'm alive? That would certainly seem like a good place to start for me.
 
  • #17
definition scope and components

Although this is Philosophy, I think it's important to recognise how limited any definition we're likely to come up with will be, at least in the next 30 to 200 years.

Our definitions are necessarily limited by our knowledge of what the universe is , and the extent to which we have looked for life.

Our search for life so far has been in only a tiny, tiny part of the total 'space' of what we otherwise know exists.

There's the vast expanses of time scales from Planck time (10-43s?) to ~10-23s - as a characteristic lifetime that we know - nothing about.

At the other end, if some 'living' thing had a lifetime of ~1 billion years (and the equivalent of a heartbeat a year), we'd be hard pressed to notice that it was 'alive', by any definition.

Life that we know is composed of baryons, a minor but not insignificant component of the universe. What about 'living' things made of the main building blocks of the universe, dark matter? dark energy?? and other minor components - 'living' things in the neutrino regime? photons??

At the level which matters, all living things we know (and hence the basis - explicit or implicit - of all our working definitions of life) live where only two of the four fundamental forces we know of reign - the electromagnetic and gravitational. Could there be some kind of 'life' among the gluons? Of course, whole Type I civilizations could rise and fall in the lifetime of the most ephemeral hadron and we'd never know it, but for the living things in such a civilization, there'd be all the time in the world.

Based on our current understanding of physics - particularly the central role of c and the HUP - 'space scale' considerations are essentially the same as the above 'time scale' considerations.
 
  • #18
I suspect that life somehow begins with consciousness, and the unwillingness to subject oneself to -- and hence exhibiting the desire to avoid -- "pain."
 
  • #19
Originally posted by Jeebus
That aside, is a neuron alive? It might be in the scientific sense, but we know it isn't quite aware of its existence and the reason behind it.

Neither is a whale, or a tree, or an insect...did you mean to put "sentient" where you said "alive"? They're not synonymous, you know.
 
  • #20


Originally posted by Iacchus32
How do I know that I'm alive? That would certainly seem like a good place to start for me.

Indeed. If there is no working definition of "life" then what right do we have to assume that I am but this computer is not? That's pretty much why I started the thread.
 
  • #21
Originally posted by Mentat
Neither is a whale, or a tree, or an insect...did you mean to put "sentient" where you said "alive"? They're not synonymous, you know.

No, I don't mean to put sentient there and I know they are not synonymous. That wasn't the point of my question. I'm curious though: Have you ever asked a whale, a tree, or an insect if it is alive? A neuron or nerve cell is a a cell, typically consisting of a cell body, axon, and dendrites, that transmits nerve impulses and is the basic functional unit of the nervous system. While only two of things you mentioned have nerve cells, I would like you to answer on how they do not know that they are alive? They function, they move, they breathe, they reproduce (in the physical context sense), and they even do daily activites or chores for working in their given environments. So I'm curious on how you can reduce the fact or even logoc that they are not "aware" (different thread) that they exist or function or animating? Given the specific, even strategic examples above; I would like you Mentat to conclude that these living, breathing, functioning beings aren't or don't know that they are "alive".
 
  • #22
Originally posted by Mentat
Indeed. If there is no working definition of "life" then what right do we have to assume that I am but this computer is not? That's pretty much why I started the thread.
And yet we as humans "know" that we're alive, in which case the working definition becomes "us." Which isn't to say that other things are not alive, just that for all intents and purposes it's the only place we can begin to consider it. At least we know this much, and that indeed life "does" exist.

So perhaps we can get past the idea of describing life in mechanistic terms, because we know it's more than that. :wink:
 
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  • #23
Originally posted by Jeebus
No, I don't mean to put sentient there and I know they are not synonymous. That wasn't the point of my question. I'm curious though: Have you ever asked a whale, a tree, or an insect if it is alive? A neuron or nerve cell is a a cell, typically consisting of a cell body, axon, and dendrites, that transmits nerve impulses and is the basic functional unit of the nervous system. While only two of things you mentioned have nerve cells, I would like you to answer on how they do not know that they are alive? They function, they move, they breathe, they reproduce (in the physical context sense), and they even do daily activites or chores for working in their given environments. So I'm curious on how you can reduce the fact or even logoc that they are not "aware" (different thread) that they exist or function or animating? Given the specific, even strategic examples above; I would like you Mentat to conclude that these living, breathing, functioning beings aren't or don't know that they are "alive".

If I understand the question correctly, you are asking me to tell you how I know that they don't know that they're alive...right? Well, if they are not sentient, then they can't know they are alive. If one uses the intentional stance (as Dennett would have one do) then one can (in principle) deduce whether something is sentient enough to know whether it is alive or not. However, the standard for being alive cannot be knowing that you are alive, since I could program my PC to "know" that it too is alive.

BTW, you said living, breathing, things...that makes them alive by default. Aside from that, is "breathing" really a criterion for living? Plants don't breath.
 
  • #24
Originally posted by Iacchus32
And yet we as humans "know" that we're alive...

Do we, Iacchus? If we can't even define "living", then how can we know that anything - including ourselves - is alive? How can we know that his distinction even exists?
 
  • #25
Originally posted by Mentat
Do we, Iacchus? If we can't even define "living", then how can we know that anything - including ourselves - is alive? How can we know that his distinction even exists?
Living is the experience of life. Are you trying to tell me you don't know what that is?

Then again I suppose this is the typified attitude which has been adopted by so many young people nowadays, who are so used to being told how to think and act, by the school system, expecting parents, etc., that they have no idea of what it means to have a life of their own.
 
  • #26
[From "Quantum Alive" on www.quantumdream.net[/URL]]

[quote] In Many-Worlds, Schroedinger's cat would now represent parallel live and dead states. Life and death are incompletely described by means of quantum mechanics, though. Attempting to define them physically recalls koans like "What is below absolute zero?" "What is north of the North Pole?" or "What occurs faster than the speed of light?" Even these may become physically realizable eventually, but the two metaphysical complements of mortality intersect only partially the truth of measurement.

The quantum itself obeys many requirements of life: e. g., taxis (particle momentum), reproduction (cascading), metabolism (beta decay), or homeostasis (thermal equilibrium). Thermodynamically interpreted death, as absolute zero, is unknown in the quantum realm. Minimum nonzero spins, particles jumping in and out of the vacuum, entire universes bootstrapped into creation, or a "dead" state resurrected through observation's action bear witness to nonclassical animation. Spiraling photons of circularly polarized electromagnetic radiation self-propagate throughout the universe, not unlike the generating potential reflected in the winding pattern of DNA diaspora.

Microscopically, life can seem eternal indeed. Our bodies incorporate the legacies of lives past. Our lungs may contain, on average, a few molecules of those breathed by Christ, Hitler or others before us. Certainly we carry a heritage of stardust, of former predator and prey. Viruses are a living/nonliving interface, an uncertainty between complements. Quanta, inherent to all things, are also universal to biological life.
In biology, the only certainties are death and taxis.[/quote]
 
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  • #27
Originally posted by Iacchus32
Living is the experience of life. Are you trying to tell me you don't know what that is?

I'm trying to remind you that a plant does not know what that is, but is still called "alive".

Then again I suppose this is the typified attitude which has been adopted by so many young people nowadays, who are so used to being told how to think and act, by the school system, expecting parents, etc., that they have no idea of what it means to have a life of their own.

LOL! I'm the one being told what to think? I thought it was you that believed in a distinction that you can't even properly define. I'm asking the open-minded questions here.
 
  • #28
Originally posted by Mentat
I'm trying to remind you that a plant does not know what that is, but is still called "alive".
In terms of what I have been taught of the existence of life, way back when (as far back as Jr. high school I believe?), is that it's biological, and it all begins at the cellular level. Thus beginning with single celled orgamisms, continuing on through the plant and animal kingdoms -- indeed -- until we finally reach that which is most highly specialized and developed of all, "human beings." Surely this is as a good a place to start as any (at the cellular level) and, I think that just about sums the whole thing up. Don't you?

Or, as you seem to imply, am I missing something here?
 
  • #29
Originally posted by Iacchus32
In terms of what I have been taught of the existence of life, way back when (as far back as Jr. high school I believe?), is that it's biological, and it all begins at the cellular level. Thus beginning with single celled orgamisms, continuing on through the plant and animal kingdoms -- indeed -- until we finally reach that which is most highly specialized and developed of all, "human beings." Surely this is as a good a place to start as any (at the cellular level) and, I think that just about sums the whole thing up. Don't you?

No. I think it is inexcusably anthropecentric to think that all of life must be cellular. This is what has been holding scientists back from studying the possibility of life on completely non-Earth-like planets: They're too stuck on the "Earth life is the only kind of life in the Universe" assumption, which has no basis.

Besides, AI research and development is constantly yeilding more and more things that could just as easily be considered "living" as some primitive (yet cellular) beings on Earth.
 
  • #30
Originally posted by Mentat
No. I think it is inexcusably anthropecentric to think that all of life must be cellular.
Time to get out the fancy words huh? Well, you're the one complaining about not having a "working model" of life which, is entirely untrue. In fact, the study of life at the biological cellular level accounts for just about every form of life that we know of -- if, I'm not mistaken? But then again I'm not a biologist.


This is what has been holding scientists back from studying the possibility of life on completely non-Earth-like planets: They're too stuck on the "Earth life is the only kind of life in the Universe" assumption, which has no basis.
Who said anything about life on other planets? That isn't the same thing as saying we don't have a working model. Besides, it will probably be a long time in waiting before we can even begin to explore life on other planets. While in the meantime, why shouldn't we take advantage of the whole wealth of resources at our disposal right here on this planet?


Besides, AI research and development is constantly yeilding more and more things that could just as easily be considered "living" as some primitive (yet cellular) beings on Earth.
Says who? And why is it so necessary to create life artificially?
 
  • #31
Originally posted by Iacchus32
Time to get out the fancy words huh? Well, you're the one complaining about not having a "working model" of life which, is entirely untrue. In fact, the study of life at the biological cellular level accounts for just about every form of life that we know of -- if, I'm not mistaken?

And would you like to stay in the current state of knowledge forever? If there is life that is non-cellular, it is because "life" actually means something. If there is no life that is non-cellular, then there is no real meaning to "life", except "that which is cellular in composition". And besides, I already mentioned AI computers. They could be considered "alive" if we could just decide on what it means. But they will never attain to "life" (even if they attain to sentient consciousness!) if we stick to the cellular definition.

Who said anything about life on other planets?

I did...it's a reasonable example, I think...

That isn't the same thing as saying we don't have a working model.

It's not the same thing, but failing to discover "life" on other planets could end up being simply because we have no working definiton thereof (since this extraterrestrial life might not be cellular).

Besides, it will probably be a long time in waiting before we can even begin to explore life on other planets. While in the meantime, why shouldn't we take advantage of the whole wealth of resources at our disposal right here on this planet?

This is philosophy...we're allowed to think into the future, aren't we?

Says who? And why is it so necessary to create life artificially?

Because we can't create it otherwise. Anything "man-made" is "artificial", by definition. Besides, it is necessary because the versitility of a living, conscious, being may be necessary even in circumstance that human bodies cannot bear...and that's just one reason, I'm sure there are others.
 
  • #32
Life is consciousness

Life has a a prerequisite, consciousness. Anything that was conscious would be aware of it, on its own level of consciousness.
So using as a postulate Life is consciousness, then we can determine what is alive. The problem of determination of what is alive depends upon observation of levels. Awareness on the atomic level, denotes a type of consciousness. Conscious atoms would then denote life. So then the universe is conscious and everyting in it, its just a matter of perception.
 
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  • #33


Originally posted by Rader
Life has a a prerequisite, consciousness. Anything that was conscious would be aware of it, on its own level of consciousness.

How do you know this?

So using as a postulate Life is consciousness, then we can determine what is alive. The problem of determination of what is alive depends upon observation of levels. Awareness on the atomic level, denotes a tye of consciousness. Consciousness atoms would then denote life. So then the universe is consciouss and everyting in it, its just a matter of perception.

Is this completely speculative, or do you have something to back it up?
 
  • #34


Originally posted by Mentat
How do you know this?

Well first you could start by reading the thread https://www.physicsforums.com/showthread.php?s=&threadid=10629
especially the post of onycho.

Is this completely speculative, or do you have something to back it up?

Mentate first we need to agree on some parameters for the discussion.
Would you agree?
01=There are no proofs.
02=We are both sane and are aware of it?
03=Knowing is evidence of it.
04=Knowledge changes over time.
05=We are alive.
06=We are conscious and aware of it.`

I would like to discuss this with you read the thread and the posts first, then we can discuss the below.

Life has a a prerequisite, consciousness. Anything that was conscious would be aware of it, on its own level of consciousness.
So using as a postulate Life is consciousness, then we can determine what is alive. The problem of determination of what is alive depends upon observation of levels. Awareness on the atomic level, denotes a tye of consciousness. Conscious atoms would then denote life. So then the universe is conscious and everyting in it, its just a matter of perception.
 
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  • #35


Originally posted by Rader
Well first you could start by reading the thread https://www.physicsforums.com/showth...;threadid=10629 [Broken]
especially the post of onycho.

I saw nothing of relevance there. Onycho completely misinterpreted a quantum even, just as so many have done before him, and will do after him. It's nothing new. The fact remains that there is no proof to back up the idea that consciousness exists at "all levels" as you imply; and there's plenty of proof against it.

Mentate first we need to agree on some parameters for the discussion.
Would you agree?
01=There are no proofs.

I agree that there are no certain proofs, but that does not excuse the use of utter speculation as though it were on equal grounds with theories formed from empirical data.

02=We are both sane and are aware of it?

Define "sane"...then tell me the relevance.

03=Knowing is evidence of it.

Knowing is evidence of what?

04=Knowledge changes over time.

If you were wrong in the first place, yes. You seem to hold "knowledge" as meaning "common knowledge", or "that which everybody 'knows'". If so, then yes, knowledge does change over time.

05=We are alive.

A useless distinction, IMO, but I suppose I am alive by biological standards. I'll take the philosophical leap and assume that you too are alive :wink:.

06=We are conscious and aware of it.`

It is indisputable that I am conscious and aware of it; you, OTOH, I have no "proof" (as per point #1) that forces me to believe that you are also conscious, but I'll take it for granted.
 
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