It is said that General Montgomery kept a picture of Field Marshal Rommel on his desk. In order to outwit Rommel he had to understand how he thought. Arguing against creationists is an on-going battle, and to persuade effectively we need to understand how creationists think. Creationists will commonly refuse to believe that the living world we see around us “arose by chance”, and the scientist will reply: “But you misunderstand evolution, yes mutations happen by chance, but evolution overall is not a random process.
I was reminded of this by Tweets by science broadcaster Brian Cox, the particle physicist who is enthusing large swathes of British teenagers about science, and managing the near impossible, getting actual science content onto prime-time BBC television. Professor Cox was annoyed by a misunderstanding promulgated on BBC Radio 4′s Thought for the Day religious slot.
First, what does a scientist mean by the above terms? The mutations that are the raw material for evolution are “random”. In statistics “random” means that different outcomes have the same probability, and in this specific context “random” means that the mutations occur regardless of whether they are harmful or beneficial to the organism. There is nothing that “knows” which mutations would be harmful or beneficial, and so there is nothing that can bias the mutations towards one or the other.
Natural selection, however, is the opposite of random, it is a sieve that preferentially selects the mutations that are beneficial (organisms with these mutations leave more descendents) and preferentially rejects the mutations that are harmful (organisms with them leave fewer descendents). As Professor Cox tweeted, natural selection is non-random. The combination of random mutations and non-random selection of those mutations is the engine of evolution, the engine that adapts an organism to its environment, leading to the whole wonderful panoply of life. As summarised by Richard Dawkins: “Life results from the non-random survival of randomly varying replicators”.
If “chance” were a synonym of “random” then the complexity of today’s life would not have originated “by chance”, since it results from the highly directional process of Darwinian evolution, which is a one-way ratchet continually selecting organisms that better fit their environment.
But is that really what people mean by “chance”? Well, no. In common parlance, “chance” is not a statement about probability, it is statement about intent and design. A “chance outcome” is one that no-one intended. The most salient aspect of a “game of chance” is not so much randomness but that crucial elements are not under conscious control, in contrast to, say, chess. If you say “I bumped into my friend Alex by chance”, you are not making a statement about the probability of your meeting, you are saying that neither of you had planned or intended it.
Thus the primary definition of “chance” is (e.g. from Oxford Dictionaries) “the occurrence of events in the absence of any intention or design”. Does life result from a process without any intention or design? The scientific answer is “Yes”! To a scientist life’s complexity does occur “by chance”!
Replying to a creationist who refuses to accept that life arose “by chance” by talking about random and non-random process is missing the point. The creationist makes a much more profound rejection of the idea. After all, the creationist has no problem with processes that lack intelligent intervention but are still non-random and directional. For example rain water running downwards and eventually running into the sea is directional, but such processes (the creationist thinks) don’t produce complexity, they don’t produce life.
The creationist is a vitalist, he doesn’t accept that something living can arise from non-living material or from merely physical processes, whether directional or not. To him life can only arise from previous life, and ultimately from a god. “And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.” Dust alone would not have sufficed.
The creationist doesn’t accept Darwin’s Dangerous Idea that life can arise from non-life, that both living and non-living matter are physical material, obeying only physical processes, and that the difference between them is just the result of replication, replication after replication, with random variation and non-random selection of the variants.
The idea that, over vast eons of time, over billions of generations, such a process could generate complexity, is unfathomable to a creationist. It is unfathomable because his brain is a product of that process, produced to do a job of promoting more replication, and thus his brain’s intuition is tuned to understanding changes that can occur within human lifetimes, not to understanding the eons of Earth’s deep time.
Thus the creationist intuitively rejects the idea that Darwinian evolution can produce complexity, when in truth it is the only process that can produce complexity of the degree seen to dazzling magnificence in Earth’s life. To a creationist such complexity could only have arisen by intelligent purpose.
In saying that “life could not have arisen by chance” it is not the presence of randomness that the creationist is complaining about, it is the absence of intention and purpose. And thus a response about random and non-random processes can only be a small part of the reply.