Fillet of a fenny snake,
In the cauldron boil & bake;
Eye of newt and toe of frog,
Wool of bat and tongue of dog,
Adder's fork and blind-worm's sting
Lizard's leg & howlet's wing,
For a charm of powerful trouble,
Like a hell broth boil and bubble.
Macbeth Act IV, Scene 1
The crone throws the wing of a bat and the eye of a newt into the cauldron, mixes it up, and voilà, you have the emergence of some mystical and immaterial "protection" or "love" or "safe trip" or "powerful trouble" spell or charm.
Likewise, take the physicalist. That crone, Mammy Nature, mixes a few billions neurons, synapses, and some firing c-fibers, into that cauldron called your noggin, and voilà, you have the emergence of some mystical and immaterial mind with beliefs and intentionality and thoughts.
When appeals to the "mustbebraindidit" argument are made, I'm going to point out that this has a name: The bat wing and eye of newt fallacy.