Thanks for sending me off to read Biology without Consciousness. It helps me understand where you are coming from and the vehemence with which you espouse the theory. Philosophical writers have a tendency to treat other theories with scorn that may not be as common in other fields.

I would have to place myself clearly in the category of soft reductionist. I agree that there may be some phenomena which does not reduce to physics, but am proceeding on the presumption that this will have to be proven and not simply assumed. And, as Efron points out there is no limit on how long this process should be allowed to proceed.

As to science, it seems to me that there are two approaches to science which both have their value.

One is in the identification, classification and measurement of objects and phenomena. This is the naturalist view of the world. The scientist endeavors to produce of catalog of what exists and what it does.

The other is is in the determination of how these objects and phenomena happen, what are the causes and effects, with the presumption, faith if you would call it, that complete understanding of things down to the lowest components will be determined.

An interesting example of the two differences came when Dr. Richard Feynman took a 'sabbatical' from Physics. He had done some studies on rat muscles and was giving a talk to biologists. He started by naming the muscles and was interrupted by the audience who said "we know all that" He was astonished that they would trouble to learn the names of all the muscles. This was a clash between the naturalist and the physicist.

Now you could take the view that the naturalist view of science is the only valid one. That we can only validly look at what exists, classify it, and determine the character of its actions; that we can not reduce those actions to simpler causes. This is the "What hath God Wrought" school. It looks at existence without solving the problem of creation.

When you look at the problem of creation, of what is the source of the natural world then there is a component of faith that such a source actually exists and can be identified and understood. Unlike observable phenomena, underlying causes are less evident. While there is much to understand, this process has yielded a vast degree of success where phenomena that were previously understood via the naturalistic approach have been identified as chemical processes, and as Efron comments with scorn, chemical processes reduced to physics. It works. The more we study these things the more we understand them. And we’ve learned a lot since the 1960s.

But we may one day fail. We may find phenomena with no physical cause. Nevertheless, unless we are going to limit ourselves to the naturalistic approach and simply observe and classify, we have to have a tool for analysis and that tool is the expectation that there are identifiable causes. Anytime you seek understanding there is a component of faith that understanding is possible.

Now we move to consciousness and the mind. In the intervening years since the cited essays our understanding of the mind its link to consciousness has continued, through experiments with brain stimulation, much deeper understanding of the chemistry and how conscious processes can be chemically effected. Functional magnetic resonance imaging (fMRI) is increasingly able to tie conscious activity to electrical processes in the brain. Understanding of consciousness in the 1960s was mostly a matter of observation. Increasingly we can “get under the hood”.

How could consciousness arise from inanimate matter? That's, of course the big question. My answer, and other's as well, is complexity.

I've spent the last 50 years working with computer programming. Developing software starts with very simple functions and building more complex ones. Then building more complex ones on top of those, this process can continue without limit.

But it's still just following set rules, isn't it? Yes and no. Back in the 1970's I spent a couple of weeks working on a simple chess playing program. It was primitive by the standards of the day, let alone today. It was easy to beat. But it was hard to beat by trying to predict the result of the algorithms, they were too complex. You had to play chess to win. The ability to build a device that that level of unpredictability so easily gave me a glimpse of what could be done if you increase the complexity by many orders of magnitude. As the algorithms become increasingly complex the ability to predict outcomes increases. And we actually put great effort into deliberately making our constructions predictable. But that’s slipping away.

We are on the edge of passing the Turing test, introduced in 1950 which set a level for artificial intelligence that it could interact with a human and the human couldn't tell the difference. Would it be conscious? Now we are back to the problem of whether we are more than simply complex algorithms running on vastly parallel processors. It there is no way for an observer to detect a difference, does a difference exist?