水泵啟動式財政 Pump Priming 新帕尔格雷夫经济学大
Daniel Dennett: Intuition Pumps and Other Tools for Thinking
Tools for pondering imponderables
“THINKING is hard,” concedes Daniel Dennett. “Thinking about some problems is so hard that it can make your head ache just thinking about thinking about them.” Mr Dennett should know. A professor of philosophy at Tufts University, he has spent half a century pondering some of the knottiest problems around: the nature of meaning, the substance of minds and whether free will is possible. His latest book, “Intuition Pumps and Other Tools for Thinking”, is a précis of those 50 years, distilled into 77 readable and mostly bite-sized chapters.
“Intuition pumps” are what Mr Dennett calls thought experiments that aim to get at the nub of concepts. He has devised plenty himself over the years, and shares some of them. But the aim of this book is not merely to show how the pumps work, but to deploy them to help readers think through some of the most profound (and migraine-inducing) conundrums.
As an example, take the human mind. The time-honoured idea that the mind is essentially a little man, or homunculus, who sits in the brain doing clever things soon becomes problematic: who does all the clever things in the little man’s brain? But Mr Dennett offers a way out of this infinite regress. Instead of a little man, what if the brain was a hierarchical system?
This pump, which Mr Dennett calls a “cascade of homunculi”, was inspired by the field of artificial intelligence (AI). An AI programmer begins by taking a problem a computer is meant to solve and breaking it down into smaller tasks, to be dealt with by particular subsystems. These, in turn, are composed of sub-subsystems, and so on. Crucially, at each level down in the cascade the virtual homunculi become a bit less clever, to a point where all it needs to do is, say, pick the larger of two numbers. Such homuncular functionalism (as the approach is known in AI circles) replaces the infinite regress with a finite one that terminates at tasks so dull and simple that they can be done by machines.
Of course the AI system is designed from the top down, by an intelligent designer, to perform a specific task. But there is no reason why something similar couldn’t be built up from the bottom. Start with nerve cells. They are certainly not conscious, at least in any interesting sense, and so invulnerable to further regress. Yet like the mindless single-cell organisms from which they have evolved (and like the dullest task-accomplishing machines), each is able to secure the energy and raw materials it needs to survive in the competitive environment of the brain. The nerve cells that thrive do so because they “network more effectively, contribute to more influential trends at the [higher] levels where large-scale human purposes and urges are discernible”.
From this viewpoint, then, the human mind is not entirely unlike Deep Blue, the IBM computer that famously won a game of chess against Garry Kasparov, the world champion. The precise architecture of Mr Kasparov’s brain certainly differs from Deep Blue’s. But it is still “a massively parallel search engine that has built up, over time, an outstanding array of heuristic pruning techniques that keep it from wasting time on unlikely branches”.
Those who insist Deep Blue and Mr Kasparov’s mind must surely be substantially different will balk at this. They may well be right. But the burden of proof, Mr Dennett argues, is on them, for they are in effect claiming that the human mind is made up of “wonder tissue” with miraculous, mind-moulding properties that are, even in principle, beyond the reach of science—an old-fashioned homunculus in all but name.
Mr Dennett’s book is not a definitive solution to such mind-benders; it is philosophy in action. Like all good philosophy, it works by getting the reader to examine deeply held but unspoken beliefs about some of our most fundamental concerns, like personal autonomy. It is not an easy read: expect to pore over some passages more than once. But given the intellectual gratification Mr Dennett’s clear, witty and mercifully jargon-free prose affords, that is a feature, not a bug.