Biologists usually think of life in terms of the ability of a system to harness energy from the environment to grow and to reproduce. However in Stanislav Lem's book 'Solaris' there is a vivid description of an exoplanetary ocean that doesn't grow or reproduce and yet communicates with human visitors and "feels" alive. So if we adhere to the principle 'you know it when you see it' then perhaps Solaris is alive. Therefore, my question is: if life is not necessarily made of cells, DNA and proteins, then what is it? Is there a more philosophical understanding of what life is?

  • 3
    Hi Sergei, welcome to Phil SE. We do not answer questions about definitions of terms here, even of philosophical terms, as they are already answered elsewhere meta.philosophy.stackexchange.com/questions/2934/… In this case see SEP plato.stanford.edu/entries/life
    – Conifold
    Aug 19, 2016 at 6:24
  • Hi @Conifold. Thank you for your comment. I didn't know that questions about definitions are not being answered here, although I will of course respect the rule. SEP is good, thank you, yet conclusions are focused largely on cellular and nucleic acid based life, and thus doesn't answer my question of what life could mean in broader context, such as an alien ocean, for example. I went ahead and removed the word "definition" from my question, in case it helps to improve it. Anyway, if this question doesn't fit Philosophy SE, it is of course worth closing/removing it.
    – Sergei
    Aug 19, 2016 at 7:07
  • 1
    Check out Jeuken's article link.springer.com/article/10.1007/BF01556737: "The biological definition is based on the phenomenon of life, the appearance, and considers the molecular structure and functions of a cell. The philosophical definition regards the being and it is proposed to consider life as transcendental". I took the liberty to edit in more philosophy into the question, hope it works for you.
    – Conifold
    Aug 19, 2016 at 8:08
  • Thanks @Conifold, I appreciate your edit as I agree it makes the question clearer, and I will for sure try to get hold of the second article you linked to. The concept of life as transcendental is intriguing.
    – Sergei
    Aug 19, 2016 at 8:32
  • Aristotle had a number of works on biology, that while are scientifically incorrect may have a philosophical cross over. Have you checked those out yet?
    – Dave
    Aug 20, 2016 at 22:23

5 Answers 5


Helmuth Plessner in his Die Stufen des Organischen und der Mensch. Einführung in die Philosophische Anthropologie from 1928 (!) [The Levels of the Organic and Man, Introduction to Philosophical Anthropology (unpublished as english translation).] proposes a philosophy of nature where the basic category of life (in phenomenological terms) is transcending its own borders from within and outside-in, and therefore having its border.

This is thought to be the basic destinguishing feature of life: Non-living nature does not have its border as part of its own (membranes, skin, etc). For 'dead things', the border is simply the nothing between two different mediums, not belonging to either of them. Living beings, as having their border, posit themselves within an environment, they have a 'positionality'.

The notion of border is summarised in Krüger, Hans-Peter (2007): 'The Second Nature of Human Beings: An Invitation for John McDowell to discuss Helmuth Plessner’s Philosophical Anthropology', Philosophical Explorations 1:2, pp. 107–119 as follows:

What do we imagine as a living phenomenon? In contrast to stones or other inorganic materials, life makes an impression as though it could stand or move in itself and from itself. In such imaginations of a living phenomenon, we presuppose that the living being has something like its own border (membrane, skin, or medium). Two directions of activity are made possible by this border: from the inside to the outside, and vice versa. Internally, the border enables differences between organs or between a core and a periphery. Regarding the environment, the border allows a selective opening of the body. One can imagine that the border could be folded internally, and at the same time, that his internal folding permits a selection of the environment, a selection in accordance with the internal differentiation. Plessner called this phenomenon ‘maintaining a position’, or in short ‘positionality’. Positionality means: a being has a relation both to itself and to others, thanks to its border. (p. 116)

Plesssner secures this (and the other categries he establishes for each level of the organic) by appling the methods of phenomenology, hermeneutics and transcendental philosophy all together, including the contemporary state of the art biologists' empirical experiments, and by this methodologically avoiding the anthropologic circle, i.e. defining categories and insight only on the basis of the specifically human (see Foucault's episteme of the modern times, but written decades earlier).

To apply your example of Lem's: With communicating, reacting to the environment and probably even having self-consciousness, the ocean would possibly even qualify for the highest level, under the name of (but explicitely not excluding other life-forms and species) the human.

  • Thanks Philip, but I find it hard to accept the border argument, because why can't we say that a rock has a border? There're beautiful rocks with structure, when their insides look different from outer layers. Regarding Lem's Solaris I also feel that it can be considered alive on the basis of consciousness. However there many unconscious beings that are alive, for example plants or mushrooms. And there is also a question if all conscious things are alive, because if one day AI software will pass a Turing test, then it might be said to be conscious, and yet it is questionable if it is alive
    – Sergei
    Aug 21, 2016 at 1:34
  • @Sergei: The point is not if something can be said to have 'a border' in the sense that there is something at the outlines of an object and something different inside it. The question is if the border is something 'passive', or if there is continuous transcending of this border (without changing it) at work. Especially the direction 'from within' is hardly a thing a stone can perform. And of course, consciousness is on the highest levels. The lowest is plants and protozoons.
    – Philip Klöcking
    Aug 21, 2016 at 5:46
  • what you are describing sounds like a "membrane" or "skin". By this definition many viruses are not alive, as many of them are not surrounded by any membrane of their own. Also, mitochondria has it's own membrane with active transport, but mitochondria is not considered to have life of its own.
    – Sergei
    Aug 23, 2016 at 22:12
  • @Sergei: First, if you are asking for definitions that go beyond biology, it is not surprising that they occasionally do. Viruses are in fact often not defined as life by biology as well, btw, whereas mitochondria show most of the signs of (biological!) life. Second, it is hard to sum up a book of hundreds of pages within one post without letting it become overly long. I do not really understand where your comment is pointing at.
    – Philip Klöcking
    Aug 24, 2016 at 15:35
  • This has a separability problem. If a species or a virus (though not a single virus molecule, the whole system) is a form of life, then the boundary is very problematic -- you would have to define such a thing as a collection of life-forms or as non-life. If it isn't, then is a slime-mold or a bacterial colony a lifeform or a collection of them? I really like the line of psychology that proceeds from here, simplified for presentation in folks like Ken Wilbur, but as a basic definition of life, it has a certain continuous/atomic problem that I think cannot be bridged.
    – user9166
    Aug 25, 2016 at 17:51

I haven't read Solaris and hardly know where to go with this question. It touches upon so many essential questions in philosophy.

You are basically asking about a definitional limit between life and non-life, biology and physics, which are often described as two different types of causality. The classic, if outdated, text on this from the physics standpoint is Schrodinger's "What Is Life?" Which suggests crystals as a borderline case. An idea which remains scientifically open.

On the other hand, the philosophical idea of a pure, inhuman "system-environment" differential is best described by Luhmann and other "systems" theorists, who are not really interested in "life" as some essential boundary.

However, your description of the "sea" in Solaris seems problematic. If it just "abides" as a self "in itself" without erasing memory and reproducing, then it does seem to be missing an essential quality of life. It is just some mythical god who endlessly exists. Rather meaningless.

I suspect that such an entity could not actually "communicate." Part of the definition of "communication" entails finite, separated selves. And "finite"means mortal. I suspect this "sea" was not thought out with philosophical consistency.

To go further into the problems here would be hard work, and I am very lazy and not terribly knowledgeable. I hope this little bit helps.

  • Hi Nelson, thanks for your comment. I am interested in helping to search for extraterrestrial life. And I am not satisfied with current biological definitions that are really just based off the single or multicellular life on earth (growth and proliferation concepts, etc). So I just gave Lem's Solaris as an example of that there may be entirely different life forms out there, but I am not arguing that this what I am looking for to understand. In general without us understanding what life is philosophically we may miss it on exoplanets
    – Sergei
    Aug 21, 2016 at 6:21
  • @Sergei, you might wanna look up the concept of Carbon chauvinism. Aug 22, 2016 at 5:36
  • @robertbristow-johnson thanks for your comment. I didn't know of the term "Carbon chauvinism" but it seems to similar the point that I am trying to understand. Although, note, it is conceivable to have carbon-based life that chemically can be very very different from animal/plant/fungal/bacterial/viral life on earth, so we may still have hard time identifying it.
    – Sergei
    Aug 23, 2016 at 22:16
  • it's certainly conceivable, but not all things conceivable are possible. better check up with some biochemists or microbiologists (ya know, DNA and protein people) about what alternative carbon life might be. Aug 23, 2016 at 22:36

How about a clearer answer from inside biology?

Framings like the Gaia movement of James Lovelock would rather see life equally at the level of the individual cell or body and at the level of an entire species, an ecosystem, or the whole planet. If you look at biology from that direction, 'grow and reproduce' is a biased version of the normal biological criterion, colored by our notions of progress.

For those larger things, growth may be basically impossible, and reproduction is extremely rare and perhaps pointless. (How would Earth grow? Why would it bother to consider a bigger version of itself better? It surely does not need to beget another planet.)

The criterion for living becomes self-directed homeostasis, instead. You can simplify that down to the ability to heal or adapt, rather than to grow or reproduce.

The emphasis on systematically displacing entropy (directing energy) for a given goal that arises naturally and is not imposed from outside remains the central part of the definition, the goal itself is just more general.


I recently read an article which may be a good starting point for a meta answer if you are trying to make a formal argument.

Life is anything that grows and eventually dies, i.e., ceases to proliferate and be cognizant. Can we say that viruses, for example, are cognizant? Yes, insofar as they react to stimuli; but they are alive essentially because they reproduce and grow. Computers are non-living because even though they can cognize, they do not develop biologically (grow), and cannot produce offspring.

  • Thanks @Dave for great link, many interesting opinions there. As to the point of the text that you quoted I disagree because viruses do not grow. If we take a particular spices of virus then all specimens are all exactly the same size. There is never a baby virus that grows, a viral particle doesn't grow, instead it is being assembled (it can also be said that it self assembles itself) to be right away of the final configuration that is capable of infecting
    – Sergei
    Aug 21, 2016 at 1:18

Good question.

Aristotles notion of what constitutes life is that it has a soul; this shouldn't be thought of in terms of the Christian/Islamic/Judaic conception, but something that is capable of 'moving' itself, and capable of perception amongst other capabilities. He explores it in De Anima, so one can think of the soul as that which animates.

Given this notion, then the sea in Solaris would constitute life; it moves itself - look at the surface of the sea - it moves; and it obviously is capable of perception, as its communicating with humans; still, it seems to me that its like the world-soul or the world become soulful.

  • thanks for introducing Aristotel's notion. I think it's spot on, although unfortunately seems to be hard to apply to something that we don't already know to be alive...
    – Sergei
    Aug 23, 2016 at 22:32
  • @serfei: I think the perception element probably does, in so far as it relates to consciousness, but we wouldn't typically think of plants as being conscious; the notion of self-motion is more interesting, and could possibly be taken as having a family resemblence to self-organisation; anyway, I just wanted to throw in what a different and older tradition thought about this question... Sep 5, 2016 at 22:48

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .