Derek asked:

Hello, I am reading Paul Churchland’s eliminative materialism article and he talks about those who argue against eliminative materialism using Leibniz’s Law commit a fallacy, however I cannot determine that fallacy, can you help? Thanks.

Answer by Jürgen Lawrenz

I have not read Churchland’s article, but he had a run-in with Leibniz in his book Seat of the Soul, Engine of Reason, when the issue was also eliminative reductionism, so I will assume that the issue is similar or the same. In that book Churchland deals with sense impressions by vector analyses, e.g. computer models of the colour spectrum, taste sensations and so on, and utilises Leibniz’s metaphor of the mill to accuse the philosopher of fallacious thinking.

Leibniz’s used his illustration to show that the idea of making thoughts visible is based in a misapprehension of what thought ‘is’. His mill is a factory floor full of wheels, belts and pulleys, and he makes the perfectly reasonable point that you can see them turn, push and pull, but you will not see any immaterial (=metaphysical) outcome, such as thoughts.

Translating this metaphor into a present day situation, start your motor car engine and go to watch the pistons, carburettor, fan belt in operation. What you will not see is the energy being generated. We are so used to speaking of energy that we associate some real quality with it, but it is after all only a manner of speaking, in other words, something metaphysical. You only know that there is energy because it causes a certain motion in mechanical parts of the engine.

Now Churchland contradicts this by giving us a model of how the ‘mind’ analyses sense impressions. His device of ‘vector analysis’ can be seen in action any time you open the colour generator in your computer or when you enlarge a picture on your computer screen, when you can see how certain colours are produced by the juxtaposition of differently coloured pixels. These are examples of eliminative reductionism. In this case, it is white light being ‘reduced’ by the division into its constituent parts. Re-assembling them gives you white light again.

When you contrast these two procedures you can see at once where the fallacy lies. Not with Leibniz, but with Churchland. He completely ignores what you and I can experience any day, namely that there are common phenomena that cannot be reduced. Nor are they explicable in materialistic terms. You can’t have half a thought or half an energy. You can’t have material atoms adding up to a thought, and what energy really ‘is’ still remains anyone’s guess.

But Churchland is perfectly content with the thought that eliminative materialism is the one and only road to complete knowledge of just about everything. But until this can be proved with thoughts and energy (among many other irreducible phenomena), this position is philosophically untenable. So the boot is clearly on the other foot. If there must be a fallacy, it is altogether in the courts of those who push reductive materialism beyond its limits of applicability.

This is Leibniz’s point: eliminative reductionism implies the divisibility of the objects of research. If they are colours, mechanical vector analysis might be useful for computer programmers, but reveals literally nothing about the way a person has the experience of colour. You might take note of the fact that Churchland ignores (as he must) that human beings invariably associate other mental and emotional qualities with colour experiences, e.g. you might ‘like’ a particular shade of blue and be enraged by a purple spot in the middle of a green wall. Another person may have different likes and dislikes. How would you like to reduce those? (Some scientists of course attempt precisely this kind of reduction, babbling about (unproved) chemical processes at the back of every such phenomenon).

In short, eliminative reductionism is a method, nothing else. As such it has limitations. To ignore those and seek to bowl readers over with blunt assertions of ‘fallacy’ is neither courteous nor supportable from actual knowledge.

Let me give you one more example to clinch this point. How can you detect the chemical processes that give life to a blade of grass? Easy: you rip it out of the soil and crunch it up. Then you can see all the chemical elements neatly lined up for scrutiny. Except for one thing: the grass is now dead. So the very element you were looking for has disappeared. Lesson: life is an irreducible quality. In this, as in many other indivisible features of existence, reductive materialism is an inappropriate method of study.