Definition of Life

What is the universal definition of a Living System?

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Understanding the definition of life is important because it shapes human decisions on a macro and micro scale.

Let me give you a simplified example, so that we understand my question. For example, if we view only some things as alive (like a baby) and other things as dead (like a river). Then, I may spill the poo from my WC to the river. If I don't know that the river is alive and how it is connected to the ecosystem, I won't know that I'll be drinking my poo at some stage, because the same water from the river will enter my water well. This is already happening with plastic in the ocean and micro-plastics eaten by the fish, and the fish eaten by humans. Ha!

So, how do we define "life" and "alive"?

Child categories: Meta-Biomimicry.

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Christopher Adami has given this definition of life: "Life is a property of an ensemble of units that share information coded in a physical substrate and which, in the presence of noise, manages to keep its entropy significantly lower than the maximal entropy of the ensemble, on timescales exceeding the "natural" timescale of the decay of the (information-bearing) substrate by many orders of magnitude.". I think it is a rather precise and pragmatic definition of life, worth looking deeper into it, and understanding every the meaning of every word in it. Here is a simulation of life, illustrating the definition: demo.

In the context of a river as the flow of liquid over crevices per se, it is not alive by itself, because its "natural decay" (⇡) is not significantly (not many orders of magnitude ⇡) dependent on it exchanging information with other units. We don't call "Silk Road" alive, just because people use it to move goods through it, and it affects the ecosystem, however, the "Silk Road" (as pathway) may be playing an important role in making something alive, like the Sun (as energy source) does.

"Definition of life is based on processes and storing information within physical subtrates." ~ C. Adami

Based on C. Adami video you shared, which is about "life" in the context of technology, I wonder how our relationship to technology change if we see it "alive"? Perhaps we would be more intentional.

It seems to me that there may be a variety of Life definitions based on the point of view.

Are we looking from a biological point of view? Physics? Math? Economical point of view? Philosophical? Spiritual dimension?

I'm curious to discuss all such points of views here in this thread.

One of point of views comes from a system thinker Fritjof Capra. He asks asks "What are the essential characteristics of life at the biological level? What are the defining characteristics of living systems?" and then he points to cells (membrane + metabolism) and Networks and Self-Generation (within a boundary of its own making) as the basic pattern of organization of all living systems."


Well, a definition is useful from the mathematical point of view, is if it provides an equivalence class, in other words, if it provides necessary conditions and sufficient conditions for something to be "it".

Sufficient conditions question: "What do we need to see in it that we would consider it to be 'life'?"

Necessary conditions question: "What are all the things that we can remove from it, so that we still consider it to be 'life', yet removing anything else from it would make it considered not to be 'life'?"

The intersection of sufficient conditions and necessary conditions usually is the defining characteristics, that are essential. So, I'd suggest seeking for them and when looking at someone's characteristics, trying to figure out what are these sufficient and necessary conditions.

Some say that entire Universe had become alive because of us, and we are its eyes. I think this is over-holistification, with some pratical utility (for example, in defining existential risk), but otherwise with little explanatory power to explain what makes 'life' be 'alive'.

    : Ruta
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