you never know what that boulder might be thinking

Joe Carter thinks he's found the core bizarritude at the heart of materialism:

...we are unable to clearly determine whether our thoughts are being produced by our desk, our chair, our TV, or our brain. After all, they are all composed of matter and matter is one. It's weird but is it wrong?

This is a problem for materialism? Spiritual dualism posits the existence of disembodied psyches that can exist even after brain death. If the brain isn't a necessary component of the mind, then what's to stop a boulder from having memories, wishes, or desires? How does dualism exclude animists from the table, except by special pleading? Or, if dualists are able to refute animism, by what non-arbitrary standards?