question explained!

in response to the meagre amount of (highly appreciated) comments in response to the question I asked in my post (first hour in school), I shall attempt a better explanation.

(Those not interested, please skip, and remember that not all my entries (in fact, most are not) are about philosophy!)

in philosophy of mind, there are 2 main schools - physicalism/materialism and dualism. The first thing to bear in mind is that these are just terms that are used to refer to certain beliefs about the world and the nature of our minds. In order to be clear in discussions, the definitions of these terms tend to be a little technical, and that is why some people understandably find it difficult to understand.

Now this is (one way of defining) what physicalism/dualism holds:

Does the physical nature of the world logically necessitate its mental nature?

Ok. Just hang on and read on. I'm going to explain the terms, and then give a layman's description.

physical nature (of the world) - the objective world as discovered in the sciences, which can have several levels of description, eg. brains, cells, neurons, proteins, DNA, carbon molecules, atoms, electrons, stones, planets, and so on... Also includes the functions of such physical objects, their configurations, arrangements, interactions, etc.... You get the general idea.

mental nature - traditionally what we regard as the experience of our minds. This includes thinking, sensing, willing, feeling, and so on. For example, the sight of a blue sky, the feel of a velvet suit, the smell of freshly cut grass, the spicyness of chilli, the sound of waves crashing upon jagged rocks; emotions like the feeling of anger, the pangs of jealousy, the delight at seeing a loved one, the nostalgia while looking at old photos; the act of willing something, deciding something, or believing something; religious/spiritual experience of worship, praise, contrition and so on.

Physical nature tends to be regarded as objective. If E=mc2 is true, then it is true no matter who is investigating this fact, or whether anyone knows it. On the other hand, what characterises mental nature is the personal, subjective quality of experience (as Thomas Nagel puts it). Atoms can still be atoms whether or not there is a subject observing them. But the experience of the smell of a rose depends on there being a subject to smell it.

Next, what is logical necessity? When I say that B is necessitated by A, it means that B logically follows from A. It means that once I have A, I cannot deny B. Consider the following example:

P1. All triangles are 3-sided figures.
P2. S is a 3-sided figure.
C. Therefore, S is a triangle.

Here, we see that once we say that S is a 3-sided figure, it is logically necessary that S is also a triangle. There is NO WAY that S can be 3-sided without being a triangle.

Similarly, when we consider the above question:

Does the physical nature of the world logically necessitate its mental nature?

If you are a physicalist, you answer 'yes', and that means that all our mental experiences are FIXED by the physical structure of our bodies and of the world. It means that, given a certain configuration of your brain, there is a certain mental experience that you must have.

For example, if now you are having a visual experience of a red apple, and some scientist discovers that you current brain is in a state, say state ABC. Then the physicalist would say that whenever your brain is in state ABC, you MUST necessarily be having the exact same visual experience of a red apple.

What the physicalist says, in effect, is that in any possible world, if there were someone with the exact physical structure as you, which goes through the same physical changes and so on, then that person must necessarily have the exact same kind of mental life as you.

Ok, now on to the dualist position. As mentioned, the dualist answers 'no' to the question. Now, this means that the dualist thinks that it is possible in theory to have another world where everything physical is exactly the same as ours, down to the last atom, but where the mental life is different. For example, we could have a world of zombies, or machines, constructed exactly like humans, with the same chemical/biological make-up, but without consciousness.

In short, the dualist thinks that the mental is not completely determined by the physical. The dualist does not deny that the mental is caused by the physical, e.g. when I stub my toe, I feel a pain (because my nerves transmit the physical information to my brain, causing the firing of some neurons, etc). What the dualist denies is that mental life and experience is fully determined by physical life, not only in our world, but in any possible world.

Phew! Having said that, I hope I have not scared off my entire readership. For the brave souls who have read all the way and hopefully achieved a new level of understanding (and a headache), do feedback. :)