Does any interaction necessarily imply emergence in physics and chemistry?

Question

I would prefer to limit the discussion by the fields of classical (not quantum) physics as well as chemistry. I wonder if the concepts of «emergence» and «emergent properties» bring anything new into these fields (sounds a wee bit stupid, but bear with me for a moment).

On one hand, it is only too easy to come up with rather convincing illustrations, for example, the system of two stars orbiting their centre of mass obviously possesses new qualities compare with the same two stars taken separately. Similarly, the properties of solution of two or more chemicals may be qualitatively different from those of its constituents.

However, using vernacular of physicists and chemists, one may say that the new properties of these two examples are nothing else but manifestations of interaction (not necessarily one conveyed by electromagnetic or gravitational force, the interaction between solution constituents is an interaction in broader sense of word). Moreover, one may be tempted to say that interaction and interacting systems are the primary subjects of study in physics and chemistry, because everything interacts in this or that way with everything around. Of course, in practice, we can consider some systems to be isolated in some sense. But is there anything emergent about such systems? So, if interaction necessarily implies emergence, then the latter notion becomes of secondary importance because all non-trivial properties resulted of interaction of any kind should be considered to be emergent.

I am not trying to be casuistic and I very much understand that in reality the concept of emergence has rather serious explanatory potential and, being such, can come in handy in studying behaviour of many systems including physico-chemical ones. But I feel confused when reading something like «emergent properties are absolutely fundamental», because this notion seems to be a mere corollary, an ancillary concept to that of interaction. That makes me wondering if emergence has any philosophical meaning when applied to the said disciplines (that being said, it seems to be useful in, say, biology or psychology, because in many cases it is not that easy to define the meaning for the term «interaction» in these field). Is there a fallacy in my line of thoughts?

Answer 1

... because this notion (emergence) seems to be a mere corollary, an ancillary concept to that of interaction.

A common beleif of modern science (after the scientific revolution) was that everything in nature would eventually be explained as a composition of interractions of it's parts. This beleif is enclosed in the concept of meterialism, which supposes that "nothing exists except matter and its movements and modifications". In common language materialism generally means "a tendency to consider material possessions and physical comfort as more important than spiritual values". These two concepts say in fact the same thing: nothing more exists than what you see.

Contrary to this, Eastern philosophies and "religions?" are characterised by the fact the they consider the totality of all things (ex. Tao) as fundamental and not as the by-product of the interractions of the parts.

Without any doubt the Western-way-of-thinking has lead us to great technological advancements. But currently we have come across huge obstacles that we cannot overcome with the traditional way of thinking.

For example you cannot explain chemical interractions by relying to plysics interractions. You cannot explain biological interractions by relying to chemical interractions. You cannot explain mental interractions by relying to biological interractions etc. In other words, the scientific fields cannot be unified using the same terminology, entities and concepts. It's like when you go one level up, new properties "emerge", it's like every system has something more that it's sub-systems.

So, we have to accept this as a fact, and thus the concepts of "emergence" and "emergent properties" are gaining ground inside the scientific community.

Answer 2

Another way of wording this question is, are there interactions which DON'T produce emergent behaviour? To which I would say, probably not, with the possible exception of very very weak interactions - for example, how normal matter and dark matter are theorised to very weakly interact through gravity. But even that might have some kind of emergence to it, so... maybe, in general, all interactions have something emergent about them.

Answer 3

• A general method in science is to isolate the object under consideration from the “rest of the world” – as far as it is possible. Then one first studies the isolated objects, and later the interaction of different objects.

• An example from physics is to study first the free theory, e.g. to solve the Dirac equation for the free electron. And to study in a subsequent step by quantum electrodynamics the interaction of light and matter. Here we have new phenomena like the creation and annihilation of particles.

  In chemistry an analogous method is to investigate first the properties of the elements themselves, and subsequently the properties of chemical substances like molecules.

• Apparently in both cases, the interaction of the components produces systems with different properties than the components in insolation. Basic concepts are “free object” and the “system of interacting objects”. I completely agree with you.

• The concept of emergence is a secondary concept: Often the system shows properties which one did not expect from considering its components in isolation.

  E.g., under standard conditions hydrogen and oxygen molecules are gaseous, while the compound system water is liquid. Sometimes one can explain the new property of the system by the properties of its components, sometimes one cannot. In the latter case there is no epistemic reduction possible.

  I agree with you to consider emergence “a mere corollary, an ancillary concept to that of interaction”.

Answer 4

There are two different concepts of emergent behavior, which we may call weak and strong. The weak notion is not very interesting; it's hard to define exactly what weak emergent behavior is, but it generally involves a property that isn't an obvious consequence of underlying interactions like the way that temperature arises out of the motion of molecules. However, even though it isn't immediately obvious that temperature would arise that way, there is a causal story based on simple physical laws to explain why it does. A lot of people seem to think this is what emergent behavior is, but like I said, it's not very interesting, so when a philosopher talks about emergent behavior, you can usually assume this is not what he means.

The more interesting notion, strong emergence, is when a behavior arises that cannot be fully explained using simple physical laws and the interaction of the parts. Life is a common example of this. Some philosophers and biologists have gone back to an older theory of life which holds that life is not fully explainable just in terms of atoms and the basic laws of physics. They hold, in effect, that there are one or more additional laws of nature, something like, "when the complexity of a system of organic molecules gets above a certain level, then this new behavior X appears", where X is something that is not a result simply of normal physical processes.