Sunday, 5 August 2012

Once Again on Uniqueness of Life

In my most recent note on principal differences between chemistry and biochemistry I stressed that biological processes were not limited to their chemical aspects:

Life = Chemistry + Cybernetics

The note concluded that because life and artificial information processing systems have so much in common, we can infer that life has also been designed and implemented by intelligence. Upon reading the note, my Russian colleague argued that my conclusion was far-fetched because life is unique and we therefore have no right to make such conclusions. Here I lay out my arguments a bit further to make my case clearer.

In what sense is life unique? Of course, its chemical side isn't. Leaving artificial systems out of the equation for the moment, the uniqueness of life is in cybernetic control on top of physicality, borrowing the expression from David Abel. In non-living nature cybernetics is not observed. Inanimate matter does not steer a system through different states towards better utility. Inanimate nature is driven only by laws, not by rules. On the other hand, cybernetic control is based on the existence of rules that prescribe which of potential states of an arbitrary system will be chosen next. The choice is made in order to optimise a goal function. That said, an important thing to keep in mind here is that the rules determining the behaviour of the system in two states S1 and S2 are indifferent to the constraints, which are the same in either state.

However, if we look to artificial information processing systems, we will notice their profound commonality with biosystems: either is controlled in order to maintain or drive the system towards a goal state. At the same time, non-living nature is inert (indifferent) to rules or goals.

Rules vs Constraints

Let us clarify this by considering games. Regardless of which cell a chessman occupies on the board, gravity acts upon it in the same way. In any of the 64 cells the constraints on its motion that are determined by the physical laws are exactly the same. The meaning of moves within the board is determined only by the rules and exists as such only in the context of the game. From the point of view of the law of gravity rules have no meaning. In other words, that the knight moves "Г"-wise, while the bishop moves diagonally cannot be explained by the existence of friction, gravity and the reaction force from the board acting on the chessmen.

The situation is absolutely the same with living organisms driven by rules written and interpreted as instructions for the ontogenesis of replicating cybernetic systems functioning in the context of physico-chemical constraints (laws). Biosystems are preprogrammed to maintain the goal state of the dynamic equilibrium, i.e. homeostasis. The reading/writing of genetic instructions during replication is executed using specific interpretation rules which are already known.

The fact that to interpret material symbols (codons) as part of transcription/translation of the genetic code biosystems employ this particular protocol cannot be explained exclusively by the physico-chemical properties of molecules participating in these processes. Information processing cannot be reduced to the physical aspects of information transfer. Likewise, the meaning of the note you are now reading can be conveyed not only through the internet but also via printed media or orally as a lecture.

It is cybernetics that complex artificial systems and biological systems have in common

As we said earlier, cybernetic control (i.e. rules that steer a system towards states of better utility) is what unites artificial information processing systems and life. This common feature allows us to conclude by induction that life is also an artefact, in full accordance with scientific rigour. Refusal to admit this obvious commonality between artificial systems and organisms is based on a priori philosophical commitments:

"Life has been intelligently designed and implemented?! It is impossible just because it is impossible."

Here is where science per se reaches the demarcation line giving way to world views.


D. Abel, Is Life Unique?
D. Abel, The First Gene.