A good definition of life can be found here.
From a physical standpoint, a living organism is a collection of interacting electrons and nuclei that jointly solve the many-body problem. They move each other striving to attain minimum potential energy configurations. These energetically favorable configurations are reached by the formation of chemical bonds, i.e. molecular orbitals in which valence electrons rest on two or more atoms simultaneously.
When the valence electrons form chemical bonds, they fall into the potential wells created by the nuclei. In the process, they transform potential energy into kinetic energy and mechanical work. This work is used to arrange the participating atoms into well-ordered molecules.
In inanimate matter, the interacting valence electrons and nuclei rearrange atoms only within separate molecules. It happens because in regular chemical reactions different molecules are disconnected from each other and move independently.
The living matter is different: A living cell is essentially one big macromolecule, in which all the molecules are orderly arranged and are connected to each other. In this situation, the constructive actions of the falling electrons transmit to the neighboring molecules. The reconstructions of the chemical bonds occur collectively. All the interacting electrons and nuclei coordinate their efforts. Jointly, they generate large collective reconstructions, in which relatively large molecular aggregates move with respect to one another in orderly ways.
In living cells, these orderly reconstructions perform so-called vital functions. With their help, the organism extracts nutrients from the environment, distributes them across its own body, controls their chemical conversion, creates new functional structures, and integrates them into its own reconstructing body. Likewise, the organism uses its own orderly reconstructions to remove used parts from the body.
Overall, the living organism is involved in its own constant renewal. It replaces used elements with fresh elements in order to produce new actions aimed at its own regeneration. With all this, the orderly reconstructions of the living body do not destroy its structure. Instead, they restore it. The constructive actions of the organism may also cause its growth and reproduction.
From a physical point of view, life is a self-sustaining collective chemical/mechanical transformation. A living organism is an arranged evolving condensed matter body that sustains the process of chemical bond building thanks to its ordered mechanical reconstructions.
Chemical Condensation
A living biological cell synthesizes high-molecular-weight products from simple precursors. From the point of view of chemical evolution of matter, it condenses, i.e. it builds additional chemical bonds and creates a larger and better-interconnected condensed matter body. A living cell is a piece of chemical condensate continuing chemical condensation.
The condensing body of the living organism executes autonomous motions and reconstructions. These motions are caused by the active atoms that build new chemical bonds. In a well-ordered condensed body, these motions combine into large collective reconstructions.
These reconstructions operate at many spatial scales. At each of these scales, the organism manipulates its parts in orderly ways. An independent organism appears at the cellular level, when the reconstructions loop into a self-stimulating circulation: The mechanical reconstructions produce new active atoms, which cause new mechanical reconstructions. Life exists for as long as the organism produces new active atoms.
A living organism is an arranged evolving condensed matter body that sustains the process of chemical condensation thanks to its ordered mechanical reconstructions.
Autonomous Behavior
The electrons that form new chemical bonds can be regarded as the elementary living-like (active) agents. They are the elementary sources of “free will”, since they cause the autonomous motions of the living body. This section explains how they coordinate their efforts and create collective actions.
The condensed body is an obstruction for the acting agents: Other atoms and existing chemical bonds block any motion and effectively inhibit the individual agents’ actions. An agent may perform an action only with the permission from the condensed body. For that, the condensed body must execute a reconstruction that removes some of the obstructions.
The evolving condensed matter body that fully controls the behavior of every active agent becomes a large “collective active agent”. It has a “collective will”, which subjugates the wills of individual active agents. The individual active agents never do what they want. Instead, they execute the collective will of the group.
The collective reconstruction
The collective reconstruction of the evolving condensed body proceeds as follows: First, the body breaks some of the existing chemical bonds. This removes some of the internal obstacles, and some of the agents become excited. It appears as though the condensed body makes a spontaneous tear in itself. Then the body discharges a weaker-connected, more active, and more mobile part from itself, and moves this part along its body to a different location. The action stops when this part reattaches to the rest of the body and gets re-stitched with new chemical bonds.
This process is explained in the following manuscript. Here, we simply note that this collective reconstruction resembles local atomic reconstructions that occur at the molecular scale. They involve a removal of some (dissatisfying) chemical bonds, an atomic permutation, followed by making new (satisfying) chemical bonds. Here, the characteristic atomic permutation reappears at a larger scale; it consists of much greater number of elementary events, and takes much longer time.
A sequence of conflicting actions
Completion of a particular collective action may liberate a previously inhibited conflicting action. The evolving body could excite other agents, make another tear, and start another action. And then the next one, etc.
All in all, in the jammed evolving condensed body, instead of acting simultaneously, the individual agents queue up and operate in succession. The evolving body as a whole executes sequences of different complex actions one after another.
The Soul
Since antiquity, the ability of the living body to make its own unprovoked purposeful actions was regarded as a conspicuous sign of the soul. Here, we explain that the soul is a perfectly natural phenomenon caused by the collective interactions of charged elementary particles.
Living-like materials
There is a big class of materials driven by the process of chemical condensation. Additionally, a living-like state is observed in condensed matter experiencing surplus of chemical bonds during the process of chemical decondensation (i.e. elimination of excess chemical bonds).
The condensing or decondensing materials could be much simpler that the real biological organisms. However, they could still perform complex autonomous actions. These simpler counterparts of living organisms could be used for manufacturing artificial living-like brains.