The onset of evolutionism brought with it the concept of branching phylogenies. The branching image, so clear and succinct, has come to underlie all … - Stuart Kauffman

The famous physicist Wolfgang Pauli is said to have remarked that the deepest pleasure in science comes from finding an instantiation, a home, for some deeply felt, deeply held image.

Francisco Varela is amazingly inventive, freewheeling, and creative. There's a lot of depth in what he and Humberto Maturana have said. Conversely, from the point of view of a tied-down molecular biologist, this is all airy-fairy, flaky stuff. Thus there's the mixed response. That part of me that's tough-minded and critical is questioning, but the other part of me has cottoned on to the recent stuff he's doing on self- representation in immune networks. I love it.

In his famous book, What is Life?, Erwin Schrödinger asks, "What is the source of the order in biology?" He arrives at the idea that it depends upon quantum mechanics and a microcode carried in some sort of aperiodic crystal—which turned out to be DNA and RNA—so he is brilliantly right. But if you ask if he got to the essence of what makes something alive, it's clear that he didn't. Although today we know bits and pieces about the machinery of cells, we don't know what makes them living things. However, it is possible that I've stumbled upon a definition of what it means for something to be alive. For the better part of a year and a half, I've been keeping a notebook about what I call autonomous agents. An autonomous agent is something that can act on its own behalf in an environment. Indeed, all free-living organisms are autonomous agents. Normally, when we think about a bacterium swimming upstream in a glucose gradient we say that the bacterium is going to get food. That is to say, we talk about the bacterium teleologically, as if it were acting on its own behalf in an environment. It is stunning that the universe has brought about things that can act in this way. How in the world has that happened?