Plantinga's Modal argument against materialism

Now, when we speak of materialism, I don't mean the view that the universe as a macroscopic whole is not a material object and that there is no immaterial things such as numbers and sets and propositions. This is an argument against materialism that says that human beings like me are just material objects there is not immaterial soul. The view that there is a immaterial self supported by a material body is substance dualism and this argues for that. This argument argues from possibility, what we mean by possibility is possibility in a logical sense, it is a modal operator like necessity. a necessity would be something which exists in all possible worlds and a necessity would be like the truths of mathematics although they are not part of logic strictly speaking. There are two kinds of truths that tell us about our world, categorical and modal. Categorical saying what something IS and Modal is what Possibly, Could be, etc. So, I have the modal property of "possibly 27 years old" it may not need to be actualized, but it is still a property I got. So his argument goes like this.


That if I were a material object I would have to be my body, but it seems perfectly conceivable that I can exist when my body doesn't. There is this short-story by Franz Kafka which is called Metamorphosis, in which this fellow wakes up in the body of a beetle, I can imagine all this happening to me waking up in a beetle body while my other body is destroyed, so here I exist, but B does not.   So, lets name our body B just for the moment. It seems possible that I can exist when B doesn't. So, I have the property of possibly existing when B doesn't, but that is the modal property that B doesn't have. So me and B are not the same thing, because there will be something true of me that isn't true of B namely, possibly exists when B doesn't. This proof is justified by Leibniz's law in predicate calculus, that whatever is true of A is also true of B, so whatever property A has B has one conversely, so among the properties are modal properties, like I said earlier, possibly such and such. So if it is for A that it is possibly such and such, but it is not the case for B that it is possibly such and such than Me and B are not the same thing. I am not the same thing as my body.

Any thoughts?