I recently read this wonderful passage in John Hyman’s book Action, Knowledge and Will (pp. 18-19) where he underscores the difference between something’s being voluntary / involuntary as compared with its being intentional / unintentional:
If we are using the word ‘voluntary’ as it is normally used (and how else are we supposed to use it?) then eating, drinking, and walking by children is not always voluntary by any means. Wittgenstein ignores the difference between eating ice-cream, which is normally voluntary, and eating green vegetables, which is often not. Nor is eating always intentional. One can eat a bug in a salad without intending to, and eat nuts automatically, without even being aware of what one is doing. Children often eat the snot from their noses this way.
Not content with presenting a couple of solid examples to illustrate his point, we get a bonus example involving children eating snot, and snot from their noses no less (where else does it even come from?!)! Brilliant. Perhaps there is a lesson in there somewhere for all philosophers.