Full Idea
By interacting causally, Cartesian dualism seems to violate the conservation laws of physics (concerning matter and energy). This seems testable, and afferent and efferent pathways disappearing into thin air would suggest energy is not conserved.
Clarification
The law says, essentially, that energy cannot be created or destroyed
Gist of Idea
If energy in the brain disappears into thin air, this breaches physical conservation laws
Source
William Lycan (Consciousness [1987], 1.1)
Book Reference
Lycan,William G.: 'Consciousness' [MIT 1995], p.2
A Reaction
It would seem to be no problem as long as outputs were identical in energy to inputs. If the experiment could actually be done, the result might astonish us.