Percy writes:But I wonder if there's a way that we can structure our scientific arguments so as to appear to have purpose.
We already do. Our language is rich in words that portray purpose, so it is hard to avoid them.
We can distinguish between extrinsic purpose and intrinsic purpose. Extrinsic purpose is as seen from outside the system:
the purpose of my car is to get me from point A to point B.
Intrinsic purpose is as seen from inside, or perhaps as inferred from internal processes:
the purpose of the heart and vascular system is to transport oxygen and nutrients throughout the body.
Percy writes:This might require describing evolution in terms like, "Species want to survive in changing environments, and so they are willing to morph themselves over time by producing a variety of offspring in the hope that some will have the necessary qualities required for survival."
That would be an example of ascribing conscious purpose. I would consider conscious purpose to be a special case of intrinsic purpose. But it comes across as inappropriate in cases such as the example you gave, where consciousness is seen as implausible.
So here are two examples of purposes already used by evolutionists:
- The purpose of natural selection is to serve as a filter that removes mal-adapted genes, thus increasing the fitness of the population;
- the purpose of reproductive processes is to copy genes.
You see these implied purposes throughout discussions of evolution. When people say that a mutation is caused by an error in copying, they are implying that there is an intrinsic purpose to copy exactly. And most of the talk of natural selection optimizing fitness is implying an extrinsic purpose.
So here we are with the
Faith thread:
The End of Evolution By Means of Natural Selection. And we see
Faith arguing that, by virtue of carrying out those purposes, evolution must have a natural limit. And we see the evolutionists, myself included, arguing that evolution works very well thank you, and it works so well precisely because it fails to carry out those purposes.
It is this kind of inconsistent use of purpose language that people find confusing. The particular debate discussed in this thread is related to the same confusion. Fred Hoyle's argument was based on the same confusion.