Inmy last blog posting, I discussed the view of the relation between mind and body that’s known as substance dualism—the theory that a person’s mind and body are two different things. The body (including, of course, the brain) is a physical thing, a configuration of matter, a flesh and blood machine, but the mind is a spooky non-physical thing that is not subject to the laws and forces that govern the physical world.

If you’re attracted to substance dualism, and think that you and everyone else really are a compound of physical body and non-physical mind, then the next step is to try and explain how the two are connected. The most obvious strategy—in fact, the knee-jerk response—is to suppose that mind and body interact with each other: your body talks to your mind and your mind talks to your body on the model of a sort of metaphysical Wi-Fi. Our sense organs are the parts of our physical body that gather information about the (physical) world around us—the sights, and sounds, and smells, and feels that get woven together as the fabric of experience.

If you’re an interactionist (someone who thinks that mind and body talk to each other) you think that these sensory inputs only becomeexperiencesonce they’re transduced into information that’s transmitted to the non-physical mind. On the other side of the coin, you think that our decisions are made by the mind and then get transmitted to the body, which then does the mind’s bidding. So, as you read these words on your computer screen, what’s supposed to be happening is that your eyes are taking in the physical information, which then gets processed by your brain (still, totally physical) and then set off to your non-physical mind, where (BINGO!) you have the experience of reading and comprehending the blog posting. And when you decide to scroll down the page to read the next paragraph what’s supposed to be going on is that your non-physical mind makes the decision to scroll down and then sends the info to your physical body, which causes that body’s fingers to move in just the right way to scroll down the page.

This way of thinking about the mind-body connection is the default position among people who’ve never studied philosophy. It’s the general picture proposed by the 17th century French philosopher-physiologist-mathematician-physicist René Descartes (of “I think, therefore I am” fame). There were substance dualists long before Descartes came on the scene, and plenty more afterwards, but Descartes is especially closely associated with this philosophical theory. Think of him as “Mr. Substance Dualism.”

尽管笛卡尔式的方法对很多人来说很有吸引力，但它现在被大多数哲学家完全拒绝了。这是为什么。

一个名叫伊丽莎白·西莫恩·范·帕兰特(又名普法尔茨的伊丽莎白公主和波西米亚的伊丽莎白公主)的女人发射了一枚哲学鱼雷，击沉了笛卡尔的船。令伊丽莎白不安的是笛卡尔的说法，即非物质的事物和物质的事物会相互影响。为什么她会认为这是个问题?It’s because these two sorts of things are not supposed to haveanythingat all in common. There’s no shared territory where they can meet. But on that assumption it’s impossible for mind and body to come into contact with each other and it therefore seems impossible for things going on in our immaterial minds to make our material bodies do things, and it’s equally impossible for happenings in our fleshy bodies to generate experiences in our un-fleshy minds.

This might sound really obscure, so let me try to unpack it in a different way. Think of an abstract, non-physical object—say, the number 37. Because the number 37 is an abstract object, there are certain questions that we can’t meaningfully ask about it. Suppose that I asked you “Where was the number 37 at 2:15 PM last Thursday?” That question doesn’t have an answer. It doesn’t even make sense. It would sound completely crazy to say, for example, that the number 37 was in San Francisco at 2:15 on Thursday. How come? Well, numbers aren’t the sorts of things that can be in a place at a certain time because they don’t exist in space and time at all.

继续说，假设我对你说:“今天早上数字37踩到我的左脚，把我弄伤了。”那将是同样疯狂的曲调。数字37必须存在于空间和时间中才能砸到我的脚，我们已经证明了它不存在于空间和时间中。但更糟糕的是，数字37不是那种可以与任何物质物体接触的东西(包括我的左脚!)Of course, a block of wood or a stone sculpture that’s shaped in the form of the numeral 37 could fall on one’s foot and bruise it—but blocks of wood and stone sculptures are concrete material objects, while the number 37—the number itself—isn’t.

Now let’s get back to Princess Elisabeth’s criticism. Descartes didn’t think of the non-physical mind as an abstract object like a number, but his concept of the mind has something important in common with the number 37. Cartesian minds, like numbers, don’t exist in time and space, and that means that—just like numbers—they can’t bump up against physical objects to affect them: a non-physical mind can’t fall on anyone’s foot and bruise it any more than the number 37 can. But if all this is true—as it surely is—then how on earth could a non-physical mind “bump up” against a physical brain? And how could electrochemical impulses coursing through the mass of nerve tissue between your ears cause anything to happen in a mind that lies entirely beyond the material world?

When you really think it through, Descartes’ version of substance dualism looks more and more like a non-starter.

Nowadays, there’s a fancy name for the problem that Princess Elisabeth identified. It’s calledthe problem of psychophysical causation. Over time, there were all sorts of ways that philosophers tried to solve it. One strategy, known as “psycho-physical parallelism,” is to hold onto the dualistic idea that bodies are physical and minds aren’t, but then go on to claim that they don’t really interact but onlyseem这样做。

A parallelist would say that when you decide to scroll down the page, and your fingers make exactly the right movements, it’s not because your decision caused your fingers to move, and when you whack your thumb with a hammer and you have the experience of it hurting like hell, the physical event of the hammer mashing your thumb didn’t cause the mental event of feeling pain. So what’s supposedly going on? The physical and mental events are just perfectly coordinated, running in parallel but never touching each other. When you crushed your thumb, the agony that you felt cameafterthe crushing but didn’t comebecauseof it.

是什么导致了这种惊人的巧合呢?当然是上帝!根据这个极其奇怪的想法的一个版本，上帝在时间之初就设定了一切，让身体和精神的轨迹完美地同步，就像两个时钟被设定为显示同一时间。另一种说法是，上帝无时无刻不在工作，以确保每个人的精神状态与他们的身体状态相匹配。

心理生理平行确实解决了伊丽莎白公主的问题，但代价是巨大的。笛卡尔的二元论或许很难让人接受，但平行论者声称的解决方案则更难让人接受。

However, there is another, much more promising way to address the problem—one that the princess was attracted to and which the majority of present-day philosophers are inclined to accept. It involves trashing substance dualism completely, and arguing that mental states justarephysical states. This position (or, more accurately, collection of positions) is called “physicalism,” and will be the topic of my next piece on the中国伊朗亚洲杯比赛直播blog.