I actually exist. I know that I actually exist. I’m aware of my actual existence in such a way,that I know for sure that I actually exist. I claim here that I actually exist *because* I actually exist. My actual existence, and my awareness of my actual existence has direct consequence on my behavior here, namely writing this paragraph.
Imagine now that you know all the relevant physical facts about my body (and all relevant physical facts about relevant environment maybe). A nice physical description. According to the physicalists, there aren’t any further facts… that is the whole story.
Now imagine that I didn’t exist, but that you still have the physical description in question. In this case it would be a physical description of a potentially existing, but not actually existing person.
In that description you should still be able to see the reasons for me pronouncing – “I actually exist, I know that I actually exist, I’m sure that I actually exist… ” (the whole first paragraph of this post)
Whatever reasons those are, they aren’t related to actual existence, and even less they can be related to any direct awareness of actual existence, simply because there is NO actual existence – the thing described in the physical description doesn’t actually exist.
However, if it is not the actual existence and awareness of actual existence that are reasons for the behavior in that description, and if physicalists are right that there are no further facts about the actual me, my actual existence and my awareness of my actual existence also can’t be reasons for my actual behavior where I say “I actually exist, I know that I actually exist, I’m sure that I actually exist… etc…”.
Similar argument can be given to establish that according to physicalism, my actual existence and my awareness of my actual existence, can’t be reasons for me thinking or knowing that I actually exist.
This is silly, hence physicalism is false.