That depends on how we define "immaterial". Does energy count as matter? If not, as it seems not to, them an immaterial event is what causes your muscles to contract. Causes by the immaterial event of your brain processing and firing neurons, of which a random cascade from the brain stem happened to cause the thought required to get you to move your arm.
If energy counts as matter, then I don't fuckin know, ghosts I guess.
If energy counts as matter, then I don't fuckin know, ghosts I guess.