Inertia is mental, vital, physical, subconscient. Physical inertia can produce mental inertia, mental inertia can produce physical inertia, vital inertia almost always makes the physical lifeless and lustreless and dull, and that is inertia. Vital inertia can also infect the mind, unless the mind is very strong and clear. I have always said that the physical consciousness is the main seat and source of inertia.