That the mind is a purely physical substance.

Friends, acquaintances, total strangers, lend me your eyes. I come here to persuade you that people are souls, not just that they have them. Here are my arguments in no particular order:I. Continuity of identity through change1. If all we are is the sum of our physical parts, then we do not maintain personal identity through physical change.2. We do maintain personal identity through physical change.3. Therefore, we are not merely the sum of our physical parts.Suppose there is a wooden ship, and we replace each piece of wood on the ship one at a time until there are no original pieces of wood left, and the entire ship is made of new wood. If that happened, then you would no longer have the original ship. It would be a completely different ship.If you are not persuaded, let's press the analogy further. Let's say that we gather together the original wood that used to be part of the ship, and we assemble it into a ship that has all of the properties of the original ship before you started replacing parts. Now you've got two ships--one made entirely of new parts, and one made of all the original parts. Surely if either of these ships stand a chance of being the original, it's the one with the original parts.If you are still not persuaded, let's tweak the thought experiment a little. Instead of replacing each piece of wood with another piece of wood, let's say we replace each piece of wood with cardboard. In the end, we'd have a ship made entirely of cardboard. By now, you should be able to see that if you replace all the parts on the ship, then you no longer have the original ship.So it is with people. We are in a constant state of change, and within 10 to 15 years, we have a mostly new body.[1] If we were identical with our bodies (i.e. if we are our bodies), then none of us have been around for longer than 10 or 15 years. You yourself never were a baby. Even some of the memories you have were not your own. Rather, you inherited them from somebody else who had those experiences but has passed out of existence.But to deny that we ourselves have continued to exist in spite of our physical changes is absurd, and many counter-intuitive results follow from it. It would follow that nobody should be convicted of a crime that happened more than 15 years earlier. It would follow that you were never born and that you have no parents. It would follow that your memories are not your own. It would follow that within another 15 years, you could cease to exist without dying.Since we do maintain personal identity through physical change, it follows that we are not identical with our bodies. We are immaterial, and we animate different bodies throughout our lives.II. The indiscernibility of identicalsAccording to the law of identity, everything is identical to itself. It's just the banal tautology that A is A. Then Gottfriend Leibniz came along and explained how this banal tautology could be put to practical use. If A and B are the same entity, then they should share every property in common. Whatever is true of A is true of B and vice versa. If there is anything true of one that is not true of the other, then they are not the same thing.If the mind is the brain, or part of the brain, then the mind and the brain should have every property in common. But they don't. Here are some properties they do not have in common.1. The brain is completely open to third person observation, but the mind is only open to first person observation.2. A thought can be about something, but the brain isn't about anything.3. While dreaming, a person can have a vivid image of a green sweater in their mind, but there is no image of a green sweater in their brain.4. A part of the brain can have a certain mass and chemical composition, but the emotion associated with it (e.g. elation or grief) does not have mass or chemical composition.5. It's possible that my mind could exist even if my brain doesn't, but it's not possible for my brain to exist even if it doesn't.III. Argument from intentional action1. If we are purely physical beings, then we cannot act willfully.2. We can act willfully.3. Therefore, we are not purely physical beings.When we act willfully, our mental states have causal influence over our brains. For example, a desire for cake combined with a belief that there's cake in the kitchen can result in brain activity that sends signals to the appropriate muscles, causing you to walk to the kitchen to get cake.If we are purely physical, then the brain state in each moment is causally determined by the brain state in the previous moment.B1-->B2-->B3-->etc.Each brain state will give rise to a mental state.B1-->M1 B2-->M2 B3-->M3 etc. But all the causation happens between the physical brain states. The mind is passive. It's just an emergent property that supervenes on the brain. It doesn't cause anything. However, we have immediate and direct access to our own mental states, so we know that we are able to act out of desires and motives. That means our mental states have causal influence over our brains. But that is only possible if our minds are substances distinct from the brain. So the fact that we can act intentionally shows that we are immaterial souls. IV. The argument from reason 1. If we are not immaterial souls distinct from the brain, then our beliefs cannot be rational.2. Our beliefs can be rational.3. Therefore, we are immaterial souls distinct from the brain. If we are not immaterial souls, then every mental state we have is the direct result of a physical state in our brains. Our brains are just physical objects that obey the laws of chemistry and physics, so all of our beliefs are arrived at by blind mechanistic causes. That means our beliefs are not rational because the only way they can be rational is if they are the consequent of good grounds and sound reasoning. If our beliefs happen to be true, that is just luck because if our beliefs are caused by blind mechanistic processes in the brain, then they would result whether there were good grounds for them or not. This argument is especially powerful because it shows that any denial of an immaterial soul is self-refuting. By denying the existence of an immaterial soul, you'd be denying the necessary preconditions for rational thought which, in turn, would make your denial irrational. Pro could bite the bullet and deny my second premise, but the problem is that if he does, he will undermine his own case at the same time. He'd essentially be admitting that even his own belief in materialism is not rational.***** [1] "Your Amazing Regenerating Body" by Gaia Vince http://www.newscientist.com... "Cells That Last a Lifetime" by April Holladay http://usatoday30.usatoday.com...