Physics into physics won’t go
I’ve read Chapter 4 of Stuart A Kauffman’s Reinventing the Sacred several times in the hope that I’ll finally get the point. But I still don’t. The chapter is called The Nonreducibility of Biology to Physics. But each time I read it I end up thinking that if he’s right that biology isn’t reducible to physics then physics isn’t reducible to physics either.
Last time I focused on the word ‘function’ as it is used in biology, and tried to dissolve the conundrum Kauffman thinks he sees in it.
I now want to focus on what I see as the other main point he is trying to make in the chapter.
Several times he asks and answers the question whether a physicist could deduce the evolution of the biosphere:
One approach would be, following Newton, to write down the equations for the evolution of the biosphere and solve them. This cannot be done.
… [Another could be] to simulate the entire evolution of our very specific, historically contingent biosphere.
He gives a number of reasons why attempts like these are doomed to failure.
One is that
The biological world straddles the quantum-classical boundary. For example, about seven photons cause a rod in your retina to respond…
But if the biological world straddles the quantum-classical boundary, surely so does the physical world? I don’t understand quantum mechanics in detail, but one thing I thought I understood was that, in our current state of knowledge, we need quantum mechanics to comprehend what we think is true about the universe. And that includes what we think is true of a universe which is like ours except it has no living things in it.
He gives the example of a stray cosmic ray which causes a mutation in a genotype which then gets selected for and so adds to and changes the biosphere. But couldn’t a stray cosmic ray also have an effect on a local climactic event which then alters the path of a growing storm?
Alan Turing proved years ago that most real numbers could not be computed—that is, he showed that there was no effective procedure, or algorithm, to compute them. … If most irrational numbers [= a subset of real numbers] are not computable, … [then] there is no algorithm to generate the supposed infinite list of statements in a lower level, or more basic, language that will “reduce” a statement in a higher language to the lower one.
Thus the physicist cannot simulate the evolution of this specific actual biosphere…
…She cannot write down equations and solve for the forward evolution of the biosphere to deduce the occurrence due to natural selection of specific organs such as the heart, and she cannot simulate the evolution of this specific biosphere with its hearts…
But again wouldn’t these also have implications for storms, currents and whirlpools?
He talks of hearts and tigers being ‘real’ in that they have independent causal influence on the world. But again wouldn’t a storm or a whirlpool also count as real for an equivalent reason?
I am not trying to claim there is no difference between a storm and a whirlpool on the one hand and a heart and a tiger on the other. But I haven’t yet seen anything in Kauffman’s chapter 4 to explain why ‘emergence’ – or a particularly significant kind of ‘emergence’ – would apply to hearts and tigers but not to storms and whirlpools.
There is of course a significant difference between hearts and tigers on the one hand and storms and whirlpools on the other. We could say that hearts and tigers are living while storms and whirlpools are not. But that is not particularly helpful – we need to dig deeper.
The significant difference is that hearts and tigers are part of a self-replicating context whereas storms and whirlpools are not. Tigers are self-replicating and hearts are components of self-replicating entities. Storms and whirlpools do not replicate themselves.
© Chris Lawrence 2011.