Sunday, October 14, 2007

Skyhooks and cranes

Some one-word titles in the psychology section of the library: Solitude, Compassion, Self-hate, Laughter, Jealousy, Regret, Shame, Prejudice, Violence, Anger, Embarrassment. And that's just for starters. It seems every psychologist has carved out his or her own little niche of the human drama for close scrutiny. Of course, all of these titles are subsets of a book that could be called simply Consciousness. And, yes, here is a title that grabs our attention: Consciousness Explained, by the eminent philosopher of cognition Daniel Dennett.

For my money, I'll take a few pages of Dennett over any of titles mentioned above. He's one smart fellow. But when I had finished reading Consciousness Explained I was still hungry. The title promises way more than it can possibly deliver, given the present state of neurological studies. What's on offer in Dennett's book is not an explanation of consciousness but a plausible idea of what the explanation might eventually turn out to be.

Dennett has a penchant for audacious titles. The subtitle of Darwin's Dangerous Idea: Evolution and the Meanings of Life again bites off more than the book can chew. The meanings of life! Wow! Surely dear old Darwin himself would not aspire to that level of hubris. Monty Python can get away with The Meaning of Life as a title, but not Mr. Dennett.

But let's be fair. It is not the meanings of my life or your life that Dennett sets out to define, but the meanings of life itself, the whole grand sweep of it, ascending from the primordial slime to -- well, to you and me, the presumed pinnacles of it all. The big question is how we got here. Was our existence foreordained, drawn up as by a skyhook from the dreary world of matter into the realm of angels? Or are we the unforeseen accumulation of blind, chance mutations selected by interaction with the environment, matter lifting itself into ever greater domains of complexity, eventually into consciousness, as if by those cranes used by builders of skyscrapers that ratchet upward as the buildings rise?

There is no more deeply entrenched idea in human culture than that we are more than the sum of our parts, our bodies more than biological automatons, our minds more than fleshy computers. According to the most widely-held view, we have been plucked like ripe fruit from the Tree of Life by a power greater than ourselves (the skyhook) and allowed to participate in a grander, loftier kind of existence. For many people the skyhook is a supernatural God. For others, including some of the brightest scientists working today, some other kind of skyhook -- cosmic mind, emergent evolution, or whatever -- does the job.

Against all these skyhook philosophies, Dennett vigorously defends the Darwinian crane. It was Darwin's great insight, he says, that all of the creatures on the planet, and all of their properties -- eggs, hair, backbones, genitalia, consciousness -- could be the products of an automatic and gradual lifter, acting over eons of time, a process as patient as it was mindless. Meaning doesn't come from on high, says Dennett; it percolates up from below, from initially mindless and pointless processes that gradually acquire meaning and intelligence as they develop -- physics to chemistry to biology to mind.

This is philosophical Darwinism at its strongest. According to Dennett, not only do organisms evolve, but so does meaning. It required billions of years of life rising to new levels of functionality and purposiveness before full-fledged intentionality could appear. And just as it is hard to draw lines in the record of life and say, "This is a bird, this is not a bird," so is meaning a matter of incremental accumulation.

The strength of Dennett's thesis is the force of mind he brings to the argument. He knows his classical philosophy. He also knows his science. He is broadly knowledgeable about evolutionary biology, computer science and the science of Artificial Intelligence, three disciplines of immense relevance to his topic. He takes on his skyhook colleagues with gusto and humor; indeed, it would be hard to find a better example of the respectful rough-and-tumble of good scientific debate than you meet in a Dennett book. Every argument is up for grabs. "This book...is for those who agree that the only meaning of life worth caring about is one that can withstand our best efforts to examine it," Dennett writes on an early page, echoing Socrates ("The unexamined life is not worth living."). Anyone who does not want their dearest presumptions challenged "are advised to close the book now and tiptoe away."

Dennett's strong Darwinism is compellingly expressed. However, this humble reader is not convinced that we yet know enough about life or mind to commit ourselves solely to cranes or skyhooks. No one who is remotely knowledgeable about science doubts that life and consciousness evolved over billions of years; what is still at issue is how complexity and consciousness arise. Is natural selection enough to drive evolution toward ever more sophisticated systems? Or is there a natural tendency toward complexity and consciousness built into creation from the very beginning, a lawful natural skyhook of sorts that might be accessible to scientific description? In my mind, the issue is undecided.

What is not in doubt at the moment is the power of the Darwinian idea. So far, the crane has been far and away the most fruitful way for doing science.

Further Reading

Daniel Dennett, Darwin's Dangerous Idea.

For a look at the search for a scientific skyhook, try Stuart Kaufmann's At Home in the Universe: The Search for the Laws of Self-Organization and Complexity.

If you have not seen the Monty Python film The Meaning of Life, by all means rent or buy it. Any question as pretentious as What Is the Meaning of Life? can use a healthy dose of satire. The last sketch, "Christmas in Heaven," is worth the price of admission.

Discuss this essay and more over on the Science Musings Blog.