I know you're making the point that just about everyone should be taxed, but to make your argument even stronger: a wilderness-liver probably has equipment (including clothes, shoes), knowledge/skills discovered/invented by others and learnt via others, and was raised within society. There may be a counter-argument for some knowledge/skill as a sort of "human heritage", like language, general knowledge, arithmetic, that isn't itself created by the state or this state (though its transmission may have been) and shouldn't be taxed.

I have some sympathy for this fellow.

EDIT also, there's no reason collaboration with other individuals should necessarily attract taxation. Human collaboration predates all states.