The more recent wave of work in complexity illuminates my bootstrap idea, in that it's a nice way of talking about this funny, screwy logic where the snake bites its own tail and you can't discern a beginning. Forget the idea of a black box with inputs and outputs. Think in terms of loops. My early work on self-reference and autopoiesis followed from ideas developed by cyberneticists such as Warren McCulloch and Norbert Wiener, who were the first scientists to think in those terms. But early cybernetics is essentially concerned with feedback circuits, and the early cyberneticists fell short of recognizing the importance of circularity in the constitution of an identity. Their loops are still inside an input/output box. In several contemporary complex systems, the inputs and outputs are completely dependent on interactions within the system, and their richness comes from their internal connectedness. Give up the boxes, and work with the entire loopiness of the thing. For instance, it's impossible to build a nervous system that has very clear inputs and outputs.

The next area of significant work involves applying the logic of the emergent properties of circular structures to look at the nervous system. The consequence is a radical change in the received view of the brain. The nervous system is not an information-processing system, because, by definition, information-processing systems need clear inputs. The nervous system has internal, or operational, closure. The key question is how, on the basis of its ongoing internal dynamics, the brain configures or constitutes relevance from otherwise nonmeaningful interactions. You can see why I'm not really interested in the classical artificial-intelligence and information-processing metaphors of brain studies. The brain can't be understood as a computer, in any interesting sense, and I part company with the people who think that the brain does rely on symbolic representation.

The same intuitions cut across other biological fields. Deconstruct the notion that the brain is processing information and making a representation of the world. Deconstruct the militaristic notion that the immune system is about defense and looking out for invaders. Deconstruct the notion that evolution is about optimizing fitness to live in the conditions present in some kind of niche. I haven't been directly active in this last line of research, but it's of great importance for my argument. Deconstructing adaptation means deconstructing neo-Darwinism. Steve Gould, Stuart Kauffman, and Dick Lewontin, each in his own way, have spelled out this new evolutionary view. Lewontin, in particular, has much appreciated the fact that my work on the nervous system mirrors his work with evolution.

My fourth area of concentration — the most recent one — consists of using the same concepts to revise our understanding of the immune system. Just as conventional biology understood the nervous system as an information-processing system, classic immunology understands immunology in military terms — as a defense system against invaders.

I've been developing a different view of immunology — namely, that the immune system has its own closure, its own network quality. The emergent identity of this system is the identity of your body, which is not a defensive identity. This is a positive statement, not a negative one, and it changes everything in immunology. In presenting immunology in these terms, I'm creating a conceptual scaffolding. We have to go beyond an information- processing model, in which incoming information is acted upon by the system. The immune system is not spatially fixed, it's best understood as an emergent network.

I've also carried out empirical work corresponding to these intuitions. These ideas are incarnated into new experiments, and provide new results. For example, in classical immunology you were dealing with an external response system that was always watching out for invaders. If this made sense, the system would shrink to nothing if there were no invaders. Yet when mice are raised in milieus free from external challenge, their immune systems are normal!

Classical medicine remains baffled by the spectrum of diseases known as autoimmune diseases. Why? Because autoimmune disease is outside the paradigm of immunology. There's nothing to vaccinate against; there's no bacteria coming from outside. It's something that the system does to itself. AIDS is a dramatic case of the deregulation of this coherent emergent property, much like ecological dysfunctioning. People think AIDS is an infection. This is, of course, true, but not true in the sense that once the system is infected with AIDS it triggers a condition of self- destruction of the immune system. HIV triggers a deregulation, which then amplifies itself and becomes its own nightmare. Thus when you look at the urine of an AIDS-infected patient, less than 5 percent of the dead lymphocytes are HIV-infected.